Source Mechanism and Tectonic Analysis of 06 May 2022 Mw 5.4 Khuzdar Earthquake along Western Boundary of the Indian Plate

doi:10.21203/rs.3.rs-1961149/v1

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Source Mechanism and Tectonic Analysis of 06 May 2022 Mw 5.4 Khuzdar Earthquake along Western Boundary of the Indian Plate

https://doi.org/10.21203/rs.3.rs-1961149/v1

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published 11 Oct, 2023

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On May 06, 2022 an earthquake of M5.4 occurred in NW of Khuzdar (Baluchistan), Pakistan. This event caused damages to infrastructure and collapsed several mud houses, according to local news agencies. On the same day, an earthquake of a similar size (M5.4) which is 230km away from the Khuzdar earthquake occurred in Dalbandin, Baluchistan. Both of these earthquakes were independent and have not appeared to be related with each other. The 2013 Awaran earthquake of magnitude 7.7 has been the largest event within this region, located 70 km away from a recent event. The recent seismicity within the Khuzdar area might be the post viscoelastic relaxation the of Awaran earthquake having the NE-SW nodal plane as the fault plane. To understand the faulting style and tectonic setting, moment tensor inversion was performed using local seismic data. The mechanism of this event was strike-slip (sinisteral faulting style) and associated with Ornach-Nal strike-slip fault. Based on 38 events focal mechanism solutions from the global Harvard Centroid Moment Tensor (CMT) of the Khuzdar region depict NW-SE orientation of SHmax direction. Reduced stress tensors obtained from formal stress inversion are then divided into two subsets (thrust and strike-slip) on basis of their stress homogeneity. The present-day stress state confirms, the oblique convergence of Indian and Arabian Plates beneath Eurasian which is subjected to a transpressional tectonic environment. A lower b-value (0.7) and accelerated earthquake sequence were observed in the Khuzdar region before this event. The spatial distribution of b-value depicts the lowest value in this region, before the occurrence of the Awaran earthquake. Although high differential stress was exhibited in this region but large has not occurred. These stresses were transferred to the western part, where the Awaran earthquake has been occurred.

Focal Mechanism Solution

Stress inversion

Ornach-Nal Fault

b-value

Earthquake Triggering

On May 06, 2022 at 11:21 (P.S.T), an earthquake of M5.4 was recorded near Khuzdar, Baluchistan province of Pakistan. The epicenter of this earthquake (26.80⁰N/66.21⁰E) was Aurnaji town (Khuzdar), while its estimated focal depth was 25 km (Fig. 1). This area is considered to be one of the most seismically active zones in the country. This event caused severe ground shaking within the epicentral vicinity and was felt by nearby regions of Iran, Afghanistan and India. According to a local news agency, at least 80 houses completely collapsed and nearly 300 homes retain small damages (The Dawn, 07 May 2022).

Another earthquake on the same day occurs near Dalbandin province, Baluchistan which was a shallow-focus (depth ~ 61 km) earthquake in the Arabian plate that is subducting under Eurasian Plate. Source faulting style of that event was normal mechanism consistent with the local tensile environment at the upper surface of the bending plate. On basis of different locality and source mechanism with that of the Khuzdar earthquake, the delayed dynamic stress triggering might be involved, but such type of analysis was not performed in this study.

The region is seismically active and has always been a source of greater earthquakes. Tectonically, the studied region is located at the junction of three major tectonic plates: Eurasian, Arabian and Indian Plate. The convergence between the Indian and Eurasian Plates lead to the formation of the world's highest mountains i.e. Hindukush, Karakoram and Himalayan ranges (Das and Filson, 1975; Molnar and Tapponnier, 1975; Molnar and Tapponnier, 1977, Tapponnier et al., 1982, Farah et al., 1984). A transform fault zone marked the western border between these plates. Towards the southern side, Arabian Plate is subducting underneath the over-riding Eurasian Plate which results in the formation of the ‘Makran subduction Zone (MSZ)’ (Farhoudi and Karig, 1977; Lin et al., 2015; Frohling and Szeliga, 2016).

A left-lateral strike-slip fault named Ornach-Nal fault, having a total length of about 300km with north-south trending seems responsible for this Khuzdar earthquake (Quittmeyer and Jacob, 1979; Lawrence et al., 1981; Barnhart, 2017). Most of the studies interpret this fault as an extension of the Chaman Fault because of its resemblance in several ways i.e. both faults mark the boundary (between Indian and Eurasian plates) and cut across the trend of fold axes in adjacent terrains (Lin et al., 2015; Frohling and Szeliga, 2016). A considerable amount of moments have been released along the Ornach-Nal fault due to their well-developed appearance and different tectonic style regions. On basis of similarity and continuity with Chaman Fault Zone (CFZ), the recurrence timespan of 500 years along the Ornach-Nal fault zone for a magnitude 7.8 earthquake was proposed (Khan et al., 2003; Frohling and Szeliga, 2016). Seismic hazard associated with this fault zone may taken as high due to alluvial deposits in the vicinity of fault zone (Bilham et al., 2007; Zaman and Warnitchai, 2012; Waseem and Khan, 2019).

Some major (M ≥ 7) historical and instrumental earthquakes occurred within Khuzdar and surrounding regions in Baluchistan are as follow; most recent one is the Awaran earthquake having Mw7.7 in the year 2013 and 70km away from a recent earthquake. The other major tectonic earthquakes were Dalbandin earthquake of Mw7.2 in 2011; Makran earthquake of Mw8.1 in 1945; Quetta earthquake of Mw7.5 in 1935, Mach earthquake of Mw7.3 in 1931; Samawani earthquake of Mw between 6.5-7.0 in 1668; Bhaminabad earthquake of Mw7.5 in 980 and Makran earthquake of Mw7.5 in 325 B.C (Quittmeyer and Jacob, 1979; Hadi et al., 2013; Ali and Khan, 2015; Khan et al., 2018). The previous seismicity along Khuzdar within 100km of the radius is shown in Fig. 2 and Table 1.

One foreshock and eleven aftershocks (Mc > 2.7; where Mc is the minimum magnitude) were recorded within three days after the occurrence of this event by the Centre for Earthquake Studies (CES) seismic network. This analysis focused on the source mechanism of mainshock of the Khuzdar earthquake and stress inversion in a complex seismo-tectonic environment. The present tectonic stress state and its changes in different structural domains of Khuzdar and neighboring areas along Baluchistan were also investigated.

The majority of tectonics along the northwestern margin of Pakistan owes to head on collision of the Eurasian with Indian plate. This oblique translation and rotation between these continental plates lead to the formation of the Chaman fault accommodating left-lateral shear. The eastern side of Indian plate comprises a series of fold and thrust belts of Sulaiman & Kirthar Ranges which are a southwestern extension of the Himalayan mountain belt (Bender and Raza, 1995; Kazmi and Jan, 1997). The Kirthar fold-thrust belt (KFTB) bounds the Sulaiman fold thrust belt (SFTB) in the south and these fold-thrust belts are separated by a tight hairpin bend of Quetta Syntaxis, Katawaz basin, containing semi-rigid mass is sandwiched between SFTB and CF and was responsible for the lobate shape of Sulaiman Range (Chandra, 1979). The significant neo-tectonic structure within this region includes Sulaiman & Kirthar Ranges, Chaman Fault Zone and Makran Range (Frohling and Szeliga, 2016).

During Eocene time, the Indian and Eurasian plates accreted sediments collectively along the western side of Pakistan and are inferred to represent a Pakistan-Iran Makran Microplate (P-IMM). The deformation and deposition of accreted sediments along the southern side of (P-IMM) subduction lead to the formation of Makran Accretionary prism/wedge and marks the offshore boundary as ‘Oman Trench’ (Burg et al., 2011). These accretionary wedge sediments scraped off the Arabian plate during the Tertiary period and stretches from Iran to Pakistan and off the coast (White, 1982; Harms et al., 1984). The termination extent of an accretionary prism is 450km in the north against the two mountain ranges of Chagai and Raskoh signifying the magmatic arc of the Makran subduction regime. The Chagai magmatic arc having Quaternary-Tertiary magnetism extends northward into Afghanistan (Shareq et al., 1977). The same arc is terminated by Chaman Fault Zone (CFZ) and Harirud Fault Zone (HFZ) from east to west and is convex towards the southward side (Farah et al., 1982).

The geodynamics of the Chagai-Makran region has a unique tectonic regime. In the south, the region is bounded by the subduction zone of the Cretaceous age. This subduction zone itself is considered to be a rare surviving feature when compared to Zagros subduction in Iran and the Indus suture zone in the Himalayas which have been eliminated by major continental collisions. Makran accretionary prism lies along the southern region and is considered to be one of the biggest accretionary prisms (Fig. 3). This accretionary prism is the hanging wall of Makran subduction zone and occupies a majority of the southern Makran region. The same accretionary wedge forms during the subduction of the Arabian plate’s oceanic portion against the overriding Eurasian plate’s Afghan Micro-continent. A transform boundary connecting the Chaman fault, Ornach-Nal fault and Murray Ridge with Owen Fracture Zone in the south and Heart fault in the north. The major structural high within the region is Murray Ridge. This onshore ridge considers equivalent to the offshore Kirthar Fold Belt in Pakistan (Clift et al., 2002; Edwards et al., 2000). The Murray Ridge is bounded by the offshore Indus Basin which serves as a major plate boundary between the Arabian and Eurasian Plates (Edwards et al., 2000).

Seismic Data Compilation and Methodology

Local seismic data from the Centre for Earthquake Studies (CES) and Pakistan Metrological Department (PMD) were used to locate earthquakes within the Khuzdar region. These seismic networks consist of 28 seismic stations, operating in the upper, central and southern parts of Pakistan i.e. Kohat-Potwar plateau, Punjab plains and big cities including Peshawar, Islamabad, Karachi, Lahore and Quetta. These seismic networks have been functional since 1976 and data is transmitted through the satellite network. The density of stations in non-uniform but threshold magnitude varies between central and southern parts of Pakistan as 1.0 and 2.7 respectively. The majority of these seismic stations are strong-motion and broadband seismometers that are operating in continuous mode and are provided data with a 24-bit digitizer.

SEISAN software package is used to determine hypocentral parameters i.e. depth, origin time and location using HYPOCENTER code (Lienert, 1991; Lienert et al., 1986; Lienert and Havskov, 1995; Ottemöller et al., 2016). Usually, the stations with good azimuthal coverage (> 180°) yield better results in focal depth and focal mechanism. Therefore, in the current analysis, only those stations are considered to have a good signal-to-noise ratio (SNR) as well as improved azimuthal coverage. The azimuthal coverage of the Khuzdar earthquake is above 150°. Similarly, having lower RMS (Root Mean Square) values for the location of the event on different seismic stations reflects a small residual between predicted and observed arrival times (Lienert and Havskov, 1995). The same recorded event has 0.8 sec residual time (RMS) based on local seismic data.

To have consistent results of source inversion and focal mechanism solution (FMS), stations having high noise, amplitude or time problems were removed. For evaluating moment tensor inversion, we used only nine out of 28 seismic stations (Fig. 4). Seismic waveform data were pre-processed using Seismic Analysis Code (SAC) software. Near subsurface effects were removed by filtering source data between 0.07 and 0.1 Hz (Fukuyama and Dreger, 1998). Seismic instrument response, mean and trend were also removed from the data. Previously available FMS within 100km of the Khuzdar event are taken from the Harvard Centroid Moment Tensor (CMT) catalog. The majority of these events were crustal depth (~ 30km) and moderate to large magnitude earthquakes (4.3–7.7). These focal mechanism solutions were further used to determine regional stresses using the Win-Tensor software suite.

Additional to waveform data and source mechanism, the previous seismicity around 50km and 100km of the Khuzdar region were also analyzed to understand spatio-temporal patterns. First, threshold magnitude for twelve years period (between 2010 and 2022) was calculated using the frequency magnitude distribution of events. Threshold magnitude is the minimum magnitude above which the catalog is complete. It is calculated using the maximum curvature method of Wiemer and Wyss (1997).

For finite region and time earthquake frequency magnitude distribution decay as a power law called Gutenberg-Richter (GR) law (Gutenberg and Richter, 1942). This is one of the most documented and general empirical relations used for earthquake studies. If N(M) is a number of earthquakes of magnitude M above Mc, then frequency magnitude distribution (FMD) can be expressed as:

$$N\left(M\right)={10}^{a-bM}$$

where a and b are productivity and relative abundance of large to small events respectively (Gutenberg and Richter, 1942; Wiemer and Wyss, 1997). These parameters describe different characteristics of an earthquake, such as if an earthquake catalog is complete for a certain time and magnitude then a can be used for earthquake recurrence time and activity rate. This is a key input parameter for seismic hazard studies. The scaling parameter b (b-value) slope of FMD is extensively used to elaborate different aspects of earthquakes (Schorlemmer and Wyss, 2005; Farrell and Smith, 2009; Gulia and Wiemer, 2010; Scholz, 2015; Khan and Mittnik, 2018; Kulhanek, Persson and Nuannin, 2018). Although for a long time window its value is close to unity (b ≈ 1) but significant variations have been observed for a shorter time window, in the range of 0.5 to 2.5 (El-Isa and Eaton, 2014). Typically FMD is affected by several factors and finding the mechanisms which are responsible for these variations is still debatable. However many studies attributed these variations to changes in stress conditions (Scholz, 2015), acoustic emissions of rocks (Scholz, 1968; Meredith, Main and Jones, 1990; Amitrano, 2003; W. Goebel et al., 2013; Martínez-Garzón et al., 2014), with depth (Wiemer and Wyss, 1997; Zúñiga and Wiemer, 1999; Gerstenberger, Wiemer and Giardini, 2001; Spada et al., 2013 and Scholz, 2015), with the tectonic regime (Schorlemmer, Wiemer and Wyss, 2005), loading rate (Amelung and King, 1997), and structural or compositional properties (Wyss, Sobolev and Clippard, 2004). Other reasons for b-value perturbations may be the degree of material heterogeneity or crack density (Mogi, 1963; Sobiesiak et al., 2007) or the change of thermal gradients (Warren and Latham, 1970).

Focal Mechanism Solution

The focal mechanism solution (FMS) is a powerful tool to investigate seismo-tectonic deformations and present-day stress patterns along tectonic regimes through seismological observations (Palano et al., 2012; Ousadou et al., 2014). These studies are important for the characterization of faulting styles and the rupture process. The seismic waveform that was recorded at a certain observatory has a linear relationship between source-time function, Green’s function and instrument response (Aki and Richards, 1980; Jost and Herrmann, 1989). The summation of many delta functions is supposed to be a source-time function when the instrument response is known of each station. Similarly, the amplitude and source-time function also depend upon the size of an earthquake (Stein and Wysession, 2002). Green’s function on the other hand depends upon the velocity model used and depicts elastic or inelastic seismic wave propagation within the subsurface. The elastic response represents wave propagation, reflection and refraction through the boundaries; whereas, its attenuation is inelastic in nature along the medium through which it propagates (Stein and Wysession, 2002). To compute Green’s function (synthetic ground motions), Kohketsu (1985) discrete wavenumber technique was used which was applicable for horizontal layered structures (Kohketsu, 1985).

FMS strongly relies upon the velocity models being used and the anisotropy of earth subsurface structures (Vavrycˇuk, 2005). To have minimum artifacts and reliable solution of inversion results, an appropriate velocity model should be selected (Kissling and Kradolfer, 1995). Two velocity structures are available for Pakistan. The regional scale (3-D) velocity model was proposed by Johnson and Vincent (2002) and developed for India and Pakistan (Johnson and Vincent, 2002). The local scale (1-D) velocity model was proposed by Soomro and Iqbal (2021) and it is validated for the regions of central and upper Indus Basin, Pakistan (Soomro et al., 2021). They used 486 events for earthquake location and suggested an average residual redunction in RMS was less than 0.9s. We used Soomro and Iqbal (2021) local velocity model, because they used the same local seismic network as that for the Khuzdar event.

To investigate the FMS of the Khuzdar earthquake, we used the moment tensor technique of Yuji Yagi and Nishimura's (2011) for source mechanism of the mainshock. It resolved the depth of the event along with fault parameters i.e. strike, rake and dip (Yagi and Fukahata, 2008). The source geometry was characterized by combining six components of the moment tensor. The model parameters, such as depth and nodal planes were taken on basis of best fit, representing the lowest variance reduction between observed and synthetic waveforms. The waveform having the best match between observed and synthetic depicts low variance. Similarly, the variance is sensitive to the amplitude and time shift of both observed and synthetic seismograms. To have maximum cross-correlation and minimum variance value, a small shifting of the seismic signal was performed. During the inversion practice, all seismograms must be assigned with uniform weights.

According to Bott (1959), all practices of stress inversion are based upon two main assumptions. The first supposition is that the stress field should be homogeneous and invariant in time and space, while the other assumption is slip occurred in the direction of maximum resolved shear stress orientation. Out of six complete stress tensors, only four parameters of σ1, σ2, σ3 (σ1-maximum, σ2-intermediate, and σ3-minimum compressive stresses, where σ1 ≥ σ2 ≥ σ3 ≥ 0) and stress ratio of principal stresses R = (σ2 _ σ3/σ1 _ σ3) with 0 ≤ R ≤ 1 resolve shear stress direction along with normal and shear stress magnitudes. Therefore, reduced stress tensors that are derived from these four parameters are constrained to focal mechanism and fault slip data (Gephart and Forsyth, 1984; Angelier, 2002). Additionally, ambiguity exists in the selection of fault plane among two nodal planes (Carey-Gailhardis and Mercier, 1987; Reches et al., 1992; Angelier, 2002; Delvaux and Sperner, 2003). To evaluate this uncertainty, a series of computer programs were available of which Delvaux and Sperner, (2003) Win-Tensor was used in this work.

The data was initially processed in the “Right Dihedron Method” within the Win-Tensor program. This technique was originally developed by Angelier and Mechler (1977) which offers approximate and initial stress tensors of the focal mechanism solutions. The results from the improved Right Dihedron are used as input for “Rotational Optimization”. This iterative method tends to minimize the misfit function (F5) of each focal mechanism solution and relies upon two components. The first component minimizes the misfit angle (α) between the modeled and observed slip on a nodal plane. The second component tends to minimize the resolved normal stress magnitude to reduce friction and maximize shear stress magnitude by leading slip on that focal plane (Delvaux and Barth, 2010). This composite function (F5) in Win-Tensor varies from 0(completely matched) to 360 (poorly matched) and is independent of the σ3/σ1 ratio.

The solutions of both nodal planes are considered equivalent within the Right Dihedron method, as they define extensional and compressional dihedron, which limit the orientation of σ3 and σ1 stresses. Thus, there was no discrimination between auxiliary and fault planes. However, the selected fault plane must have a minimum misfit value, when applying stress tensor because both planes have a different orientation with respect to applied stress. Similarly, on both nodal planes of each focal solution, we determine the best fit stress tensor within the Rotational Optimization method. Within this method, we consider the actual fault plane by applying the stress tensor to all focal solutions and selecting the nodal plane having a smaller F5 misfit value. This technique eliminates those planes having angular misfits greater than 60°, which eventually filtered data with the most compatible focal plane for each mechanism. The selected focal planes with smaller F5 misfit values were used and a new stress tensor was again computed. These steps of stress tensors are repeated until the resulting stress tensor was optimized.

The tectonic stress regime index R′ of Delvaux (1997) was followed after the final stress tensor is obtained. This stress regime index R′ ranges from 0 to 1 for normal faulting (extensional regimes), 1 to 2 for strike-slip and 2 to 3 for thrusting (compressive regimes). Lund and Townend (2007) technique allows finding the direction of horizontal principal stresses (S_Hmin and S_Hmax) as the orientation of the smallest and greatest axes of the ellipse. These orientations of axes are obtained by the intersection of a horizontal plane with a stress ellipsoid. According to the World Stress Map ranking parameter, quality factor was assigned to the final results as defined in Heidbach et al. (2010) in the form of A, B, C, D, and E where A depicts excellent and E is considered to be non-compatible data (Heidbach et al., 2010). This quality factor signifies the accuracy of stress axes along with ± 5° uncertainty for A-quality factor, ± 15° for B-quality factor, ± 20° for C-quality factor and ± 25° for D-quality factor data. The focal solutions data having a quality factor of A, B, C and D were used to have reliable stress patterns for our study. All other focal planes were filtered out for non-compatible data having uncertainty ± 35° (F5 > 35) because these data sets are not considered to be reliable for analyzing stress patterns.

The recent (06^th May 2022) Khuzdar earthquake was the largest one within twenty years of data in this region (within 50km from epicenter). This event was widely felt and caused some minor damages to building in the epicenter region. The FMS of the Khuzdar earthquake based on best fit model values is shown in (Figure 5). The event was left lateral strike-slip, correlated with that of Ornach-Nal Fault on basis of strike and slip direction. Ornach-Nal Fault is a splay of the Chaman Fault system (major transform fault in western Indian collision boundary) on basis of similar strike direction and faulting style.

The vicinity area around Khuzdar is too large and complex to evaluate the first-order stress of the entire regime. We divide the region into two main subgroups based on faulting style. The major faulting within the region corresponds to the strike-slip faulting style which reflects both the orientation of the pre-existing faults and the stress regime. The other sub-set group covers the thrust faulting style. The stress inversion results are given in (Table 2&Table 3).

Strike-Slip Regime (Zone 1)

The events within this group were marked on basis of the similarity index for uniform mechanisms. 30 out of total 43 events lie within this zone as strike-slip events. The events within this group (box) were associated with Hoshab, Chaman and Ornach-Nal left-lateral faults. The largest and most recent Awaran earthquake was the left-lateral strike-slip, the majority of this group solutions represents aftershocks triggered by the mainshock. Although there is some rotation within the compression (S_Hmax) direction of individual events but the average S_Hmax direction was NW-SE (N147⁰E) oriented. The optimized values fall in C-category for Rotational Optimization (S_Hmax 147±11.5) and Right Dihedron (S_Hmax 148.7±6.3) according to the world stress map. The seismo-tectonic stress field is categorized by a stress regime index having a ratio R′ (1.64±0.27) and obeys the limits of strike-slip events. These strike-slip faults correspond to first-order stresses which are consistent with the regional stress direction of the Indian and Eurasian Plate (Figure 7, 9).

The transpressional tectonics mainly derive the major structures in this region, addition to strike-slip, thrust faults can also be seen in the SW and Eastern direction of the Ornach Nal fault. According to Jolivet et al. (2014) shortening and major strains within this region are accumulated by these thrusts that are oriented at an oblique angle to the Ornach Nal fault. Whereas part of the shortening is also accommodated within the prism to explain rotation. They proposed that the combined effect of shortening in the accretionary wedge, due to subduction of the Arabian plate, and the shear strain along the Ornach Nal fault imposed by the Indian plate caused the occurrence of the 2013 Awaran earthquake.

Thrust Regime (Zone 2)

The stress inversion results of the eight focal mechanism solutions within this box depict a transpressional environment of the thrusting regime. Five events were neglected based upon the F-5 misfit function. The strike of these thrusts are EW in Makran range, rotated to NS direction along the Western boundary of Sulaiman range. Interestingly, these reverse faults formed the deformation front of the subduction boundary (e.g., Bernard et al., 2000; Reynolds, Copley and Hussain, 2015). The lowest dip event or westward dipping corresponds to the eastward shortening, whereas eastward dipping faults are steeper dips that may represent newly initiated thrust faults. These steeper faults were interpreted as reactivated pre-existing faults as given by Hinsch et al., (2019). There were two types of events, one with a depth of ≤ 10 km occurred within the basement of the Indian shield and another type of events with > 20 km were at the interface of the Indian shield basement. The NW-SE trending focal planes give a first-order representation of oblique convergence between Indian and Eurasian Plates. The major shortening and interseismic strain coupling are accommodated within these thrust faults in this region. The data quality of this box is comparatively average to poor (D-category). The S_Hmaxdirection is nearly oblique E-W (N122⁰E). The optimized value of Rotational Optimization is S_Hmax 122±18.1 and Right Dihedron is S_Hmax 143.8±7.2 according to the world stress map. The stress ratio R′ (2.37±0.2) obeys the limits of the thrusting regime and is associated with the Kirthar thrust belt (Figure 8, 9).

Temporal Distribution of Seismicity

To visualize frequency magnitude distribution and seismicity pattern of the Khuzdar region, earthquake data from the homogenized catalog was taken within twelve years (between 2010 and 2022) and 50km around the recent earthquake. The cumulative events distribution with their corresponding magnitudes is shown in (Figure 10). It consists of two types of a plot; one with all recorded events that were 52, whereas another with threshold magnitude correction was applied that has 31 events. The occurrence of small magnitude (majority of events i.e., three were magnitude 2.5 and 3.0) events was started nearly one year before and accelerated with time. The same pattern can’t be seen when threshold magnitude is applied.

The threshold magnitude (Mc) for the Khuzdar region was 3.7. The Gutenberg-Richter law was fitted to the data above threshold magnitude. A lower b-value (b=0.7) of GR fitting was observed for the Khuzdar region, manifesting a relatively higher abundance of large events compared to small events. The occurrence of the M7.7 Awaran earthquake in the year 2013, which is nearly 90km away from the recent event might cause a lower b-value in this region. The region was an accelerated or higher seismicity rate of ~ 4.2 events/year as compared to the average or reference seismicity (2.7 events/year) observed before the Awaran earthquake. According to Scholz (2015), the b-value is inversely proportional to stress, thus lower b-value depicts higher differential stress were exist in this region before the occurrence of the Awaran earthquake. Ornach Nal fault in the Khuzdar region possesses a lower b-value than form eastern part of the Hoshab fault at which the Awaran mainshock was located. These accumulated stresses were migrated rather than triggered large event on the Ornach Nal fault.

Spatio-temporal distribution of b-value within 50km of Khuzdar region was not possible to perform due to small data points. Thus, the data selection region was extended, so that to have sufficient events, this includes the Awaran aftershock zone too. The study area was subdivided into 10x10 km grids, b-value was calculated at each grid node by using the maximum likelihood method with a constant number of events (i.e., 60 events) and circular distance. We used the ZMAP software of Wiemer and Zúniga (1994), written in Matlab to calculate the b-value (Figure 11). The spatial distribution of the b-value depicts strong perturbation or variability in the b-value (b ~ 0.4-1.0) that might be caused by differential stress exhibited in this region. A lower b-value exists within the epicentral region of the Awaran earthquake, caused by the occurrence of aftershocks and higher stress released by the mainshock. A similar type of phenomenon such as a decrease in b-value during the aftershock sequence after the mainshock widely observed in several earthquake studies (El-Isa and Eaton, 2014). Local asperities, stress and slip heterogeneity over the rupture plane of the mainshock might be the major cause of the reduction in b-value.

The higher b-value was observed in the NE of the study area, which corresponds to the Chaman Fault zone. Which is a major transform boundary fault between the India-Eurasian plates. Major shear strain accumulation and South propagation of Sulaiman Range are being accommodated. The epicentral region of the Khuzdar earthquake has b ~ 0.7, which depicts slip asperity also exists in this region.

Partially locked and highly stressed patches over a fault plane are going to rupture in a larger event being associated with low b-values.

The stress coupling amplitudes and their direction of neighboring locked patches might cause a degree of homogenization of the stress field. If there stress amplitude and direction are similar might cause a large magnitude event. Numerical modeling suggests that as a system approaches failure, the fault plane progressively becomes more homogenized. The small ruptures progressively grow together and become larger, thus the b-value decreases.

The mainshock along with events i.e. 2, 7, 8, 10, 16, 18 and 19 depicts NS orientation which resembles Ornach-Nal fault. The faulting style changes to thrusting as we move towards the eastern side of the mainshock. The events i.e. 3, 11, 14, 17 and 28 represent the thrust mechanism and are associated with the thrusting of the Kirthar Range (Fig. 6). The remaining events along the western and northern side of the mainshock depict NE orientation and are consistent with Chaman Fault. To compute stresses, Chaman Fault and Ornach-Nal combine into a single zone name ‘Chaman Fault Zone’. This box contains strike-slip events and has an overall SHmax direction of NW-SE. The same events within this box portray the first-order of stresses when inverted for stress inversion and were fairly consistent with the movement of the Indian Plate relative to the Eurasian Plate and highlight the role of large tectonic forces in first-order stress pattern (Fig. 9) (Heidbach et al., 2016; Rajabi et al., 2017).

The lowest b-value in the Khuzdar earthquake region shows higher differential stress, but a large event (Awaran) occurred at 70km west. This might show the stress was migrated from this region to trigger the Awaran earthquake in the year 2013. After the occurrence of the Awaran earthquake, the activity rate in the Khuzdar region was constant rather than accelerated. Ornach-Nal fault is one of the major transform fault in this region where the Indian-Euroasian subduction shear stress is accommodated.

The source mechanism of the mainshock of the Khuzdar earthquake was inverted using local seismic data from CES and PMD networks of Pakistan. Moment tensor inversion of recent event depicts left lateral faulting style. The strike orientation of the fault plane was in the EW direction. The present-day configuration of tectonic stresses within the region is mostly driven by dynamics of local faults i.e. Ornach-Nal fault. This fault seems to be responsible for the current seismic event and plays an important role in deformation within the area. The stress analysis of catalog events depicts strike-slip and thrust faulting regimes. The strike-slip zonation (box) portrays a similar direction of Indian-Eurasian convergence and portrays first-order stress. The lowest slope of the frequency magnitude distribution shows a higher probability of a large event occurring in this region. Stress accumulated over the Ornach-Nal fault due to subduction of the Indian plate was migrated to trigger an earthquake on the Hoshab fault.

Data and Resources

Seismograms used in this study are taken from the local seismic network of PMD and CES. FMS of events was taken from the global CMT catalog.

Acknowledgments

The authors are grateful to the Director General (CES) and Pakistan Metrological Department (PMD) for the data used in this study. The authors are also thankful to Bilal Saif, Naveed Mushtaq and Muhammad Yousaf Khan for ArcGIS, GMT and Win-Tensor software and for improving this manuscript technical writing.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

conflict of interest

The authors whose names listed in manuscript certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.

Aki, K., and P. Richards (1980). Quantative seismology: Theory and methods. Quantative Seismology: Theory and Methods. San Francisco.
Ali M, Khan M.J. (2015) GIS based study on seismicity of Makran over 100 years. Int J of Econ Environ Geol 6(2):11–16
Amelung, Falk, and Geoffrey King. 1997. ‘Large-Scale Tectonic Deformation Inferred from Small Earthquakes’. Nature 386 (6626): 702–5.
Amitrano, David. 2003. ‘Brittle‐ductile Transition and Associated Seismicity: Experimental and Numerical Studies and Relationship with the b Value’. J. Geophys. Res.: Solid Earth 108 (B1).
Angelier, J. (2002), Détermination du tenseur des contraintes par inversion de mécanismes au foyer de séismes sans choix de plans nodaux, C. R. Geosci., 334(1), 73–80.
Angelier, J., and P. Mechler (1977), Sur uneméthode graphique de recherche des contraintes principales également utilisables en tectonique et en seismologie: La méthode des dièdres droits, Bull. Soc. Geol. France, XIX(6), 1309–1318.
Apel, E., R. Bürgmann, P. Bannerjee, and B. Nagarajan (2006). Geodetically constrained Indian plate motion and implications for plate boundary deformation, Eos Trans. AGU 87, no. 52, Fall Meeting Supplement, Abstract T51B-1524.
Arthurton, R.S., Farah, A., Ahmed, W. (1982) The Late Cretaceous-Cenozoic history of western Balochistan, Pakistan - The Northern Margin of the Makran Subduction Complex, Geological Society of London Special Publication, 10, 343-385.
Barnhart, William D. 2017. ‘Fault Creep Rates of the Chaman Fault (Afghanistan and Pakistan) Inferred from InSAR’. J. Geophys. Res.: Solid Earth 122 (1): 372–86.
Bayer, R., J. Chery, M. Tatar, Ph. Vernant, M. Abbassi, F. Masson, F. Nilforoushan, E. Doerflinger, V. Regard, and O. Bellier (2006). Active deformation in Zagros-Makran transition zone inferred from GPS measurements, Geophys. J. Int. 165, no. 1, 373–381, doi 10.1111/ j.1365-246X.2006.02879.x.
Berg, E., B.R. Lienert, and L.N., Frazer (1986). HYPOCENTER: An earthquake location method using centered, scaled, and adaptively damped least squares. Bull. Seism. Soc. Am. 76(3), 771–783.
Bernard, M, B Shen‐Tu, WE Holt, and DM Davis. 2000. ‘Kinematics of Active Deformation in the Sulaiman Lobe and Range, Pakistan’. J. Geophys. Res.: Solid Earth 105 (B6): 13253–79.
Bilham, Roger, Sarosh Lodi, Susan Hough, Saria Bukhary, Abid Murtaza Khan, and S. F. A. Rafeeqi. 2007. ‘Seismic Hazard in Karachi, Pakistan: Uncertain Past, Uncertain Future’. Seismol. Res. Lett.78 (6): 601–13.
Bott, M. H. P. (1959). The mechanics of oblique slip faulting. Geol. Mag., 96(02), 109–117.
Byrne, Daniel E., Lynn R.Sykes and D.M. Davis (1992) Great Thrust Earthquake and Aseismic Slip along the Plate Boundary of the Makran Subduction Zone; J. Geophys. Res. 97, 449-478.
Carey-Gailhardis, E., and J. L. Mercier (1987). A numerical method for determining the state of stress using focal mechanisms of earthquake populations: Application to Tibetan teleseisms and microseismicity of southern Peru, Earth Planet. Sci. Lett., 82(1), 165–179.
Chandra, Umesh. 1979. ‘Large-Scale Cenozoic Tectonics of Central and South-Central Asia: Products of Continental Collision’. Phys. Earth Planet. Inter. 20 (1): 33–41.
Clift, P., Gaedicke, C., Edwards, R., Lee, J.I., Hildebrand, P., Amjad, S., White, R.S. & Schl¨uter, H.-U., (2002). The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea, Mar. Geophys. Res., 23(3), 223–245.
Copley, A., Avouac, J. P., & Royer, J. Y. (2010). India‐Asia collision and the Cenozoic slowdown of the Indian plate: Implications for the forces driving plate motions. J. Geophys. Res.: Solid Earth, 115(B3).
Das, Shamita, and John R Filson. 1975. ‘On the Tectonics of Asia’. Earth Planet. Sci. Lett. 28 (2): 241–53.
Davies, D., J. Suppe, and F. A. Dahlen (1983). Mechanics of fold-and-thrust belts and accretionary wedges, J. Geophys. Res. 88, no. B2, 1153– 1172, doi 10.1029/JB088iB02p01153.
Delvaux, D., and A. Barth (2010), African stress pattern from formal inversion of focal mechanism data, Tectonophysics, 482(1), 105–128.
Delvaux, D., and B. Sperner (2003), New aspects of tectonic stress inversion with reference to the Tensor program, Geol. Soc. London Spec. Publ., 212(1), 75–100.
Delvaux, D., R. Moeys, G. Stapel, C. Petit, K. Levi, A. Miroshnichenko, V. Ruzhich, and V. San’kov (1997), Paleostress reconstructions and geodynamics of the Baikal region, central Asia, Part 2. Cenozoic rifting, Tectonophysics, 282(1), 1–38.
Fukuyama, E., M. Ishida, D. S. Dreger, and H. Kawai (1998). Automated seismic moment tensor determination by using online broadband seismic waveforms, J. Seism. Soc. Jpn. 51, 149–156.
Edwards, R.A., Minshull, T.A. & White, R.S., 2000. Extension across the Indian–Arabian plate boundary: the Murray Ridge, Geophys. J. Int., 142,461–477.
El-Isa, Zuhair H, and David W Eaton. 2014. ‘Spatiotemporal Variations in the B-Value of Earthquake Magnitude–Frequency Distributions: Classification and Causes’. Tectonophysics 615: 1–11.
Farah, Abul, Ghazanfar Abbas, Kees A De Jong, and Robert D Lawrence. 1984. ‘Evolution of the Lithosphere in Pakistan’. Tectonophysics 105 (1–4): 207–27.
Farhoudi, G., and D. E. Karig (1977). Makran of Iran and Pakistan as an active arc system, Geology 5, no. 11, 664–668, doi 10.1130/0091-7613(1977)5<664:MOIAPA>2.0.CO;2.
Farhoudi, Godratollah, and D. E. Karig. 1977. ‘Makran of Iran and Pakistan as an Active Arc System’. Geology 5 (11): 664–68.
Farrell, Jamie, Stephan Husen, and Robert B Smith. 2009. ‘Earthquake Swarm and B-Value Characterization of the Yellowstone Volcano-Tectonic System’. J. Volcanol. Geotherm. 188 (1–3): 260–76.
Frohling, Elyse, and Walter Szeliga. 2016. ‘GPS Constraints on Interplate Locking within the Makran Subduction Zone’. Geophysical Supplements to the Monthly Notices of the Royal Astronomical Society 205 (1): 67–76.
Fukahata, Y., and Y. Yagi (2008). Importance of covariance components in inversion analyses of densely sampled observed data: An application to waveform data inversion for seismic source processes. Geophys. J. Int., 175, 215–221.
Gephart, J. W. (1990). A fortran program for inverting fault/slickenside and earthquake focal mechanism data to obtain the regional stress tensor. Comput. Geosci.16(7), pp.953-989.
Gephart, J. W., & Forsyth, D. W. (1984). An improved method for determining the regional stress tensor using earthquake focal mechanism data: Application to the San Fernando earthquake sequence. J. Geophys. Res., 89(B11), 9305–9320.
Gerstenberger, Matt, Stefan Wiemer, and Domenico Giardini. 2001. ‘A Systematic Test of the Hypothesis That the b Value Varies with Depth in California’. Geophys. Res. Lett. 28 (1): 57–60.
Gulia, Laura, and Stefan Wiemer. 2010. ‘The Influence of Tectonic Regimes on the Earthquake Size Distribution: A Case Study for Italy’. Geophys. Res. Lett. 37 (10).
Gutenberg, Beno, and Charles Francis Richter. 1942. ‘Earthquake Magnitude, Intensity, Energy, and Acceleration’. Bull. Seismol. Soc. Am. 32 (3): 163–91.
Hadi S, Khan S.D, Owen L.A, Khan A.S, Hedrick K.A, Caffee M.W. (2013) Slip-rates along the Chaman fault: Implication for transient strain accumulation and strain partitioning along the western Indian plate margin. Tectonophysics 608:389–400
Harms, J. C., et al. (1984). The Makran Coast of Pakistan: its Stratigraphy and Hydrocarbon potential, in Marine Geology and Oceanography of Arabian Sea and Coastal Pakistan pp. 3-26, Van Nostrand Reinhold, Co., New York.
Harms, J. C., H. N. Cappel, and D. C. Francis (1985). The Makran coast of Pakistan: Its stratigraphy and hydrocarbon potential, in Marine Geology and Oceanography of Arabian Sea and Coastal Pakistan B. U. Haq and J. D. Milliman (Editors), Van Nostrand Reinhold, New York, 3–27.
Havskov, J., and B.R. Lienert (1995). A computer program for locating earthquakes both locally and globally. Seismol. Res. Lett., 66(5), 26–36.
Heidbach, O., M. Tingay, A. Barth, J. Reinecker, D. Kurfeß, and B. Müller (2010), Global crustal stress pattern based on the World Stress Map database release 2008, Tectonophysics, 482(1), 3–15.
Herrmann, R., and M.U. Jost (1989). A student’s guide to and review of moment tensors. Seismol. Res. Lett. 60(2), pp.37-57.
Hinsch, Ralph, Chloé Asmar, Muhammad Nasim, Muhammad Asif Abbas, and Shaista Sultan. 2019. ‘Linked Thick-to Thin-Skinned Inversion in the Central Kirthar Fold Belt of Pakistan’. Solid Earth 10 (2): 425–46.
Soomro, R.A., S. Iqbal, T. Iqbal, and M.A. Shah (2020). 1D Velocity model for Central and Northern Pakistan. J. Seismol. (under review).
Jacob, K. H, and R. L. Quittmeyer, (1979) The Makran Region of Pakistan and Iran: trench-arc system with active plate subduction, in Geodynamics of Pakistan, edited by A. Farah and K. A. de Jong, pp. 305-317, Geological Survey of Pakistan, Quetta.
Johnson, M., and Vincent, C. (2002). Development and testing of a 3d velocity model for improved event location: A case study for the india-pakistan region. Bull. Seism. Soc. Am. 92(8), 2893–2910.
Jolivet, Romain, Z Duputel, B Riel, M Simons, L Rivera, SE Minson, H Zhang, MAG Aivazis, F Ayoub, and S Leprince. 2014. ‘The 2013 M w 7.7 Balochistan Earthquake: Seismic Potential of an Accretionary Wedge’. Bull. Seismol. Soc. Am. 104 (2): 1020–30.
Jost, M.U., and R. Herrmann. 1989. ‘A Student’s Guide to and Review of Moment Tensors’. Seismol. Res. Lett. 60: 37–57.
Khan et al., 2008; Copley et al., 2010Argus, D., DeMets, C., R.G. Gordon, and S. Stein (1990). Current plate motions. Geophys. J. Int. 101(2), pp.425-478.
Khan S, Waseem M, Khan M.A, Ahmed, W. (2018) Updated earthquake catalogue for seismic hazard analysis in Pakistan. J. Seismol. 22(4): 841–861
Khan, M. A., R. Bendick, M. Ismail Bhat, R. Bilham, D. M. Kakar, S. Faisal Khan, S. H. Lodi, White, R. S., and K. Klitgord (1976). Sediment deformation and plate tectonics in the Gulf of Oman, Earth Planet. Sci. Lett. 32, no. 2, 199–209, doi 10.1016/0012-821X(76)90059-5.
Khan, Muhammad Yousaf, and Stefan Mittnik. 2018. ‘Nonlinear Time Series Modeling and Forecasting the Seismic Data of the Hindu Kush Region’. J. Seismol. 22 (1): 353–76.
Khan, S.A., Shah, M.A., and Qaisar, M. (2003). Seismic risk analysis of coastal area of Pakistan. Acta Seismologica Sinica. Vol. 16 No.4 (382-394). Doi: 1000-9116(2003)04-0382-13.
Khuzdar Earthquake, (2022). The Dawn News. Retrieved May 10, 2022, from https://www.dawn.com/news/1688392
Kohketsu, K. (1985). The extended reflectivity method for synthetic near-field seismogram. J. Phys. Earth, 33, 121-131.
Kopp, C., J. Fruehn, E. R. Flueh, C. Reichert, N. Nukowski, J. Bailas, and D. Klaeschen (2000). Structure of the Makran subduction zone form wide-angle and reflection seismic data, Tectonophysics 329, no. 1–4, 171–191, doi 10.1016/S0040-1951(00)00195-5.
Kukowski, N., T. Schillhorn, E. R. Flueh, and K. Huhn (2000). Newly identified strike-slip plate boundary in the northeastern Arabian Sea, Geology 28, no. 4, 355–358, doi 10.1130/0091-7613(2000) 28<355:NISPBI>2.0.CO;2.
Kulhanek, Ota, Leif Persson, and Paiboon Nuannin. 2018. ‘Variations of B-Values Preceding Large Earthquakes in the Shallow Subduction Zones of Cocos and Nazca Plates’. J. South. Am. Earth. Sci. 82: 207–14.
Lawrence, R. D., R. S. Yeats, S. H. Khan, A. Farah, and K. A. DeJong (1981), Thrust and strike slip fault interaction along the Chaman transform zone, Pakistan, Geol. Soc. London Spec. Publ., 9, 363–370.
Lienert, B. (1991). Report on modifications made to Hypocenter: Institute of Solid Earth Physics.
Lund, B., and J. Townend (2007), Calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor, Geophys. J. Int., 170(3), 1328–1335.
M. Sufyan Qazi, B. Singh, W. Szeliga, and A. Wahab (2008). Preliminary geodetic constraints on plate boundary deformation on the western edge of the Indian plate from TriGGnet (Tri-University GPS Geodesy Network), J. Himalayan Earth Sci. 41, 71–87.
Martínez‐Garzón, Patricia, Grzegorz Kwiatek, Hiroki Sone, Marco Bohnhoff, Georg Dresen, and Craig Hartline. 2014. ‘Spatiotemporal Changes, Faulting Regimes, and Source Parameters of Induced Seismicity: A Case Study from The Geysers Geothermal Field’. J. Geophys. Res.: Solid Earth 119 (11): 8378–96.
Meredith, Philip G, Ian G Main, and Colin Jones. 1990. ‘Temporal Variations in Seismicity during Quasi-Static and Dynamic Rock Failure’. Tectonophysics 175 (1–3): 249–68.
Mogi, Kiyoo. 1963. ‘Some Discussions on Aftershocks, Foreshocks and Earthquake Swarms: The Fracture of a Semi-Infinite Body Caused by an Inner Stress Origin and Its Relation to the Earthquake Phenomena (Third Paper)’. Bull. Earthq. Res. Inst. Univ. Tokyo 41 (3): 615–58.
Molnar, Peter, and Paul Tapponnier. 1977. ‘The Collision between India and Eurasia’. Scientific American 236 (4): 30–41.
Nishimura, N., and Y. Yagi (2011). Moment tensor inversion of near source seismograms. Bull. Int. Institute of Seis. Earthquake Eng. 45, pp.133-138.
Ottemöller, L., J. Havskov, and P. Voss (2016). Seisan earthquake analysis software for windows, solaris, linux and macosx.
Ousadou, F., L. Dorbath, A. Ayadi, C. Dorbath, and S. Gharbi (2014), Stress field variations along the Maghreb region derived from inversion of major seismic crisis fault plane solutions, Tectonophysics, 632, 261–280.
Palano, M., L. Ferranti, C. Monaco, M. Mattia, M. Aloisi, V. Bruno, F. Cannavó, and G. Siligato (2012), GPS velocity and strain fields in Sicily and southern Calabria, Italy: Updated geodetic constraints on tectonic block interaction in the central Mediterranean, J. Geophys. Res., 117 B07401, doi:10.1029/2012JB009254.
Panagos, P., A. Jones, C. Bosco, and P. S. S. Kumar (2011), European digital archive on soil maps (EuDASM): Preserving important soil data for public free access, Int. J. Digital Earth, 4, 434–443.
Quittmeyer, R. and Jacob K.H. (1979) Historical and modern seismicity of Pakistan, Afghanistan, northwestern India, and southeastern Iran. Bull Seismol Soc Am 69(3):773–823
Rajabi, M., Tingay, M., Heidbach, O., Hillis, R., & Reynolds, S. (2017). The present-day stress field of Australia. Earth-Science Reviews, 168, 165–189. https://doi.org/10.1016/j.earscirev.2017.04.003
Ravaut, R., D. Carbon, J. F. Ritz, R. Bayer, and H. Philip (1998). The Sohar Basin, Western Gulf of Oman: Descriptions and mechanisms of formation from seismic and gravity data, Mar. Petrol. Geol. 15, no. 4, 359–377, doi 10.1016/S0264-8172(98)00055-5.
Reches, Z. E., G. Baer, and Y. Hatzor (1992), Constraints on the strength of the upper crust from stress inversion of fault slip data, J. Geophys. Res., 97(B9), 12,481–12,493, doi:10.1029/90JB02258.
Reilinger, R., et al., (2006), GPS constraints on continental deformation in the Africa-Arabia-Eurasia continental collision zone and implications for the dynamics of plate interactions, J. Geophys. Res., 111, B05411, doi:10.1029/2005JB004051.
Reynolds, Kirsty, Alex Copley, and Ekbal Hussain. 2015. ‘Evolution and Dynamics of a Fold-Thrust Belt: The Sulaiman Range of Pakistan’. Geophys. J. Int. 201 (2): 683–710.
Scholz, Christopher H. 2015. ‘On the Stress Dependence of the Earthquake b Value’. Geophys. Res. Lett. 42 (5): 1399–1402.
Schorlemmer, Danijel, Stefan Wiemer, and Max Wyss. 2005. ‘Variations in Earthquake-Size Distribution across Different Stress Regimes’. Nature 437 (7058): 539–42.
Shareq et al., (1977) Mineral Resources of Afghanistan. (2nd ed.), Afghan Geological and Mines Survey, Afghanistan.
Sobiesiak, Monika, U Meyer, Sebastian Schmidt, H‐J Götze, and CM Krawczyk. 2007. ‘Asperity Generating Upper Crustal Sources Revealed by b Value and Isostatic Residual Anomaly Grids in the Area of Antofagasta, Chile’. J. Geophys. Res.: Solid Earth 112 (B12).
Spada, Matteo, Thessa Tormann, Stefan Wiemer, and Bogdan Enescu. 2013. ‘Generic Dependence of the Frequency‐size Distribution of Earthquakes on Depth and Its Relation to the Strength Profile of the Crust’. Geophys. Res. Lett. 40 (4): 709–14.
Stein, S., and M. Wysession (2002). An Introduction to Seismology, Earthquakes and Earth Structures:Wiley-Blackwell.
Tapponnier, Paul, GLDAY Peltzer, AY Le Dain, Roland Armijo, and P Cobbold. 1982. ‘Propagating Extrusion Tectonics in Asia: New Insights from Simple Experiments with Plasticine’. Geology 10 (12): 611–16.
Vavrycˇuk, V. (2005). Focal mechanisms in anisotropic media. Geophys J Int, 161(2), 334–346.
W. Goebel, TH, Danijel Schorlemmer, TW Becker, G Dresen, and CG Sammis. 2013. ‘Acoustic Emissions Document Stress Changes over Many Seismic Cycles in Stick‐slip Experiments’. Geophys. Res. Lett. 40 (10): 2049–54.
Warren, Nicholas W, and Gary V Latham. 1970. ‘An Experimental Study of Thermally Induced Microfracturing and Its Relation to Volcanic Seismicity’. J. Geophys. Res. 75 (23): 4455–64.
Waseem, Muhammad, Muhammad Asif Khan, and Sarfraz Khan. 2019. ‘Seismic Sources for Southern Pakistan and Seismic Hazard Assessment of Karachi’. Natural Hazards 99 (1): 511–36.
White, R.S. (1982) Deformation of the Makran accretionary sediment prism in the Gulf of Oman (North-West Indian Ocean).Geological Society, London, Special Publications, 10, 357-372.
Wiemer, S, and RF Zúniga. 1994. ‘1994. ZMAP-a Software Package to Analyze Seismicity, EOS, Transactions, Fall Meeting, AGU 75, p. 456’. In . Meeting, AGU.
Wyss, Max, Gennady Sobolev, and James D Clippard. 2004. ‘Seismic Quiescence Precursors to Two M7 Earthquakes on Sakhalin Island, Measured by Two Methods’. Earth, Planets and Space 56 (8): 725–40.
Zúniga, F Ramón, and Stefan Wiemer. 1999. ‘Seismicity Patterns: Are They Always Related to Natural Causes?’ Pure Appl. Geophys. 155 (2): 713–26.

Table 1. Previous seismicity within 100km of events having magnitude greater than 5.

Year	Month	Day	Hour	Minute	Second	Lat.	Long.	Depth	Mag.
1990	6	17	4	51	45.51	27.4	65.72	15	6.1
1990	6	17	17	17	43.16	27.3	65.55	15	5.6
1990	8	14	0	50	39.21	27.02	65.97	21	5.5
1990	9	8	19	33	18.85	27.5	66.09	28	5.5
1990	11	14	18	45	3.86	27.44	66.09	37	5.6
1992	1	20	8	58	22.55	27.4	65.99	27	5.5
1992	4	24	7	7	26.05	27.55	66.24	20	6.0
2013	9	24	11	29	47.8	26.92	65.53	13	7.7
2016	3	21	14	48	50.7	27.69	66.13	5	5.5
2017	12	6	23	41	59.9	27.22	65.8	214	5.5
2022	5	6	6	21	20.6	26.80	66.21	15	5.5

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Source Mechanism and Tectonic Analysis of 06 May 2022 Mw 5.4 Khuzdar Earthquake along Western Boundary of the Indian Plate

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