Probabilistic Seismic Hazard Analysis of Sitamarhi near Bihar-Nepal Region

doi:10.21203/rs.3.rs-475275/v1

This article presents the results of a probabilistic seismic hazard analysis (PSHA) for Sitamarhi, Bihar considering the region-specific maximum magnitude and ground motion prediction equation (GMPEs). North Bihar region is one of the seismically unstable areas in India facing several destructive earthquakes for the Himalayan Mountains that was created by the collision of Indian and Eurasian plate. The Gutenberg-Richter (G-R) seismic hazard parameter ‘a’ and ‘b’ have been evaluated by considering the available local earthquake data. Earthquake data were collected from the United States geological survey (USGS), Indian Meteorological Department (IMD), New Delhi, Seismotectonic Atlas of India (GIS 2000) within 500 km radius of the study area, and 62 seismotectonic sources were identified and considered in this study. Seismic source zones for the region have been defined based on large-scale geological features, which are used for assigning the maximum possible earthquake potential. Estimated PGA values are 0.89 g and 0.61 g for the 2% and 10% probabilities of exceedance in 50 years. The results showed that West Patna fault and Sitamarhi Fault are the two main faults, which contribute maximum in the peak ground acceleration (PGA) values for Sitamarhi region.

Seismology

Seismic hazard analysis

Spectral acceleration

Peak ground acceleration

Uniform hazard spectrum

Gutenberg-Richter recurrence law

Table 1 Details of seismotectonic sources in the study area collected from Seismotectonic Atlas of India published by GSI (2000)

Sl. No.	Sources	Fault type
1	Main Frontal Thrust (MFT)	Neotectonic Thrust Fault
2	Main Central Thrust (MCT)	Thrust Fault
3	East Patna Fault (EPF)	Thrust Fault
4	Munger Saharsa Ridge Fault (MSRF)	Subsurface Fault
5	Munger Saharsa Ridge Marginal Fault (MSRMF)	Subsurface Fault
6	Katihar Nailphamari Fault (KNF)	Thrust Fault
7	West Patna Fault (WP-SS-1)	Thrust Fault
8	West Patna Fault (WP-SS-2)	Thrust Fault
9	West Patna Fault (WP-SS-3)	Thrust Fault
10	Bhagapur Neotectonic Fault (BNF)	Neotectonic Fault
11	Neotectonic Fault (NF-1)	Neotectonic Fault
12	Neotectonic Fault (NF-2)	Neotectonic Fault
13	Subsurface Fault With Strike Slip Movement (SS-1)	Subsurface Fault
14	Subsurface Fault With Strike Slip Movement (SS-2)	Subsurface Fault
15	Subsurface Fault With Strike Slip Movement (SS-3)	Subsurface Fault
16	Subsurface Fault With Strike Slip Movement (SS-4)	Subsurface Fault
17	Subsurface Fault With Strike Slip Movement (SS-6)	Subsurface Fault
18	Main Boundary Thrust (MBT)	Thrust Fault
19	Fault (G-1)	Fault involving Basement and Cover
20	Sitamarhi Fault (SIF)	Subsurface Fault
21	Thrust Zone- 1(TZ-1)	Thrust Fault
22	Main Central Thrus- 1 (MCT-1)	Thrust Fault
23	Main Central Thrus- 1 (MCT-2)	Thrust Fault
24	Main Boundary Thrust- (MBT-1)	Thrust Fault
25	Neotectonic Fault (NF-3)	Neotectonic Fault
26	Neotectonic Fault (NF-4)	Neotectonic Fault
27	Neotectonic Fault (NF-5)	Neotectonic Fault
28	Neotectonic Fault (NF-6)	Neotectonic Fault
29	Neotectonic Fault (NF-7)	Neotectonic Fault
30	Neotectonic Fault (NF-8)	Neotectonic Fault
31	Neotectonic Fault (NF-9)	Neotectonic Fault
32	Neotectonic Fault (NF-10)	Neotectonic Fault
33	Neotectonic Fault (NF-11)	Neotectonic Fault
34	Neotectonic Fault (NF-12)	Neotectonic Fault
35	Neotectonic Fault (NF-13)	Neotectonic Fault
36	Neotectonic Fault (NF-14)	Neotectonic Fault
37	Rajmahal fault (RMF)	Neotectonic Fault
38	Santhia Bahmini Fault (SBF)	Neotectonic Fault
39	Thrust Zone-1 A (TZ-1 A)	Thrust Fault
40	Thrust Zone-1 B (TZ-1B)	Thrust Fault
41	Main Central Thrust-1 A (MCT-1 A)	Thrust Fault
42	Main Central Thrust-1 B (MCT-1 B)	Thrust Fault
43	Main Central Thrust-1 C (MCT-1 C)	Thrust Fault
44	Main Central Thrust-1 D (MCT-1 D)	Thrust Fault
45	Main Central Thrust-1 E (MCT-1 E)	Thrust Fault
46	Main Central Thrust-1 F (MCT-1 F)	Thrust Fault
47	Main Central Thrust-1 G (MCT-1 G)	Thrust Fault
48	Main Central Thrust-1 H (MCT-1 H)	Thrust Fault
49	Main Central Thrust- A (MCT A)	Thrust Fault
50	Main Central Thrust- B (MCT B)	Thrust Fault
51	Main Central Thrust- C (MCT C)	Thrust Fault
52	Main Central Thrust- D (MCT D)	Thrust Fault
53	Main Central Thrust- E (MCT E)	Thrust Fault
54	Main Central Thrust- F (MCT F)	Thrust Fault
55	Main Central Thrust- G (MCT G)	Thrust Fault
56	Main Central Thrust- H (MCT H)	Thrust Fault
57	Main Central Thrust- I (MCT I)	Thrust Fault
58	Main Central Thrust- J (MCT J)	Thrust Fault
59	Main Central Thrust- K (MCT K)	Thrust Fault
60	Main Central Thrust- L (MCT L)	Thrust Fault
61	Main Central Thrust- M (MCT M)	Thrust Fault
62	Main Central Thrust- N (MCT N)	Thrust Fault

Table 2 Seismotectonic sources and corresponding fault length, maximum magnitude, rupture length, closest distance and longest distance from the sources

Sl. no.	Sources	Fault length, L_o (km)	Rupture length, L=L_o/3 (km)	M_max	Closest distance, r_min (km)	Longest distance, r_max(km)
1	MFT	95.49	31.83	6.8	112.22	192.40
2	MCT	965.87	321.95	8.0	91.52	491.53
3	EPF	172.22	57.40	7.1	81.79	130.39
4	MSRF	199.63	66.54	7.2	147.16	157.32
5	MSRMF	137.91	45.97	7.0	161.22	255.54
6	KNF	124.42	41.47	7.0	272.46	367.47
7	WP-SS-1	63.04	21.01	6.6	21.28	42.02
8	WP-SS-2	67.81	22.60	6.7	38.42	96.00
9	WP-SS-3	61.17	20.39	6.6	107.73	160.32
10	BNF	12.40	4.13	5.8	175.54	186.76
11	NF-1	18.94	6.31	6.0	196.84	200.73
12	NF-2	30.29	10.09	6.2	181.63	198.39
13	SS-1	121.64	40.54	6.9	195.99	272.33
14	SS-2	116.15	38.72	6.9	162.63	264.73
15	SS-3	97.76	32.59	6.8	116.98	141.05
16	SS-4	170.89	56.963	7.1	182.77	337.59
17	SS-6	13.62	4.54	5.8	130.79	551.18
18	MBT	489.58	163.19	7.6	88.88	164.38
19	G-1	155.07	51.69	7.1	85.42	48.22
20	SIF	61.26	20.42	6.6	27.93	130.97
21	TZ-1	440.89	146.96	7.6	174.52	281.17
22	MCT-1	412.94	137.64	7.6	101.76	230.19
23	MCT-2	242.92	80.97	7.3	275.55	301.14
24	MBT-1	73.59	24.53	6.7	276.99	279.43
25	NF-3	8.10	2.70	5.6	196.62	196.67
26	NF-4	6.76	2.25	5.5	200.19	200.23
27	NF-5	4.82	1.60	5.3	182.02	182.04
28	NF-6	11.66	3.88	5.8	183.27	183.37
29	NF-7	19.62	6.54	6.0	175.42	194.27
30	NF-8	25.43	8.47	6.2	196.05	212.17
31	NF-9	61.24	20.41	6.6	270.15	318.57
32	NF-10	54.08	18.02	6.5	281.65	323.42
33	NF-11	33.26	11.08	6.3	321.50	364.72
34	NF-12	61.23	20.41	6.6	291.84	352.44
35	NF-13	28.25	9.41	6.2	277.98	278.35
36	NF-14	44.48	14.82	6.4	282.80	476.33
37	RMF	68.55	22.85	6.7	298.35	391.66
38	SBF	103.79	34.59	6.9	262.58	281.08
39	TZ-1 (A)	229.70	76.56	7.6	272.16	495.41
40	TZ-1 (B)	188.54	62.85	7.6	272.16	456.96
41	MCT-1 (A)	51.57	17.19	7.6	96.22	129.43
42	MCT-1 (B)	51.68	17.23	7.6	106.65	129.43
43	MCT-1 (C)	58.87	19.62	7.6	106.65	157.48
44	MCT-1 (D)	42.09	14.03	7.6	157.48	167.75
45	MCT-1 (E)	35.96	11.98	7.6	134.12	167.75
46	MCT-1 (F)	46.56	15.18	7.6	134.12	152.96
47	MCT-1 (G)	34.87	11.62	7.6	152.96	159.15
48	MCT-1 (H)	44.78	14.93	7.6	129.46	159.15
49	MCT (A)	164.47	54.82	8.0	222.91	376.44
50	MCT (B)	27.08	9.02	8.0	219.52	222.91
51	MCT (C)	16.58	5.53	8.0	205.34	219.52
52	MCT (D)	36.56	12.19	8.0	193.61	205.34
53	MCT (E)	40.91	13.64	8.0	178.06	193.61
54	MCT (F)	39.05	13.02	8.0	146.40	178.06
55	MCT (G)	53.06	17.68	8.0	146.40	150.17
56	MCT (H)	238.74	79.58	8.0	144.47	150.17
57	MCT (I)	32.86	10.95	8.0	144.47	169.82
58	MCT (J)	40.72	13.57	8.0	169.82	207.96
59	MCT (K)	33.19	11.06	8.0	207.96	225.70
60	MCT (L)	32.61	10.87	8.0	225.70	254.56
61	MCT (M)	76.99	25.63	8.0	188.99	254.56
62	MCT (N)	86.82	28.94	8.0	188.99	274.13

Table 3 Summary of earthquake events having moment magnitude (M_w) greater than or equal to 4.0

Sl. No.	Earthquake magnitude Mw range	Number of events
1	4.0 ≤ Mw < 4.1	118
2	4.1 ≤ Mw < 4.2	105
3	4.2 ≤ Mw < 4.3	127
4	4.3 ≤ Mw < 4.4	123
5	4.4 ≤ Mw < 4.5	113
6	4.5 ≤ Mw < 4.6	96
7	4.6 ≤ Mw < 4.7	84
8	4.7 ≤ Mw < 4.8	71
9	4.8 ≤ Mw < 4.9	51
10	4.9 ≤ Mw < 5.0	46
11	5.0 ≤ Mw < 5.1	41
12	5.1 ≤ Mw < 5.2	33
13	5.2 ≤ Mw < 5.3	26
14	5.3 ≤ Mw < 5.4	6
15	5.4 ≤ Mw < 5.5	10
16	5.5 ≤ Mw < 5.6	12
17	5.6 ≤ Mw < 5.7	6
18	5.7 ≤ Mw < 5.8	5
19	5.8 ≤ Mw < 5.9	4
20	5.9 ≤ Mw < 6.0	3
21	6.0 ≤ Mw < 6.1	2
22	6.1 ≤ Mw < 6.2	2
23	6.2 ≤ Mw < 6.3	2
24	6.3 ≤ Mw < 6.4	3
25	6.4 ≤ Mw < 6.5	1
26	6.5 ≤ Mw < 6.6	0
27	6.6 ≤ Mw < 6.7	1
28	6.7 ≤ Mw < 6.8	1
29	6.8 ≤ Mw < 6.9	1
30	6.9 ≤ Mw < 7.0	2
31	Mw ≥ 7.0	4

Table 4 Comparison of a and b values of the study area with nearby areas

Sl. No.	Area	Distance from study area (km)	a value	b value	References
1	Sitamarhi (present study)	0	4.36	0.85
2	Patna: Region 1 Region 2	115	5.32 4.98	0.91 1.01	Anbazhagan et al. (2015)
3	Patna: Region 1 Region 2	115	5.32 4.98	0.87 0.97	Anbazhagan et al. (2019)
4	Lucknow: Region 1 Region 2	453	4.07 3.20	0.86 0.80	Kumar et al. (2013)
5	Kanpur: Region 1 Region 2	514	5.133 6.266	0.931 1.123	Anbazhagan et al. (2017)
6	Nepal and surrounding region	126	-	0.85	Ram and Guoxin (2013)
7	Kolkata	530	2.734	0.738	Shiuly et al. (2015)

Probabilistic Seismic Hazard Analysis of Sitamarhi near Bihar-Nepal Region

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