Spatial and temporal influence of rainfall on crustal pore pressure based on seismic velocity monitoring
Crustal pore pressure, which controls the activities of earthquakes and volcanoes, varies in response to rainfall. The status of pore pressure can be inferred from observed changes in seismic velocity. In this study, we investigate the response of crustal pore pressure to rainfall in southwestern Japan based on time series of seismic velocity derived from ambient noise seismic interferometry. To consider the heterogeneity of the area, rainfall and seismic velocity obtained at each location were directly compared. We used a band-pass filter to distinguish the rainfall variability from sea level and atmospheric pressure, and then calculated the cross-correlation between rainfall and variations in S-wave velocity (Vs). A mostly negative correlation between rainfall and Vs changes indicates groundwater recharge by rainfall, which increases pore pressure. The correlations differ between locations, where most of the observation stations with clear negative cross-correlations were located in areas of granite. On the other hand, we could not observe clear correlations in steep mountain areas, possibly because water flows through river without percolation. This finding suggests that geographical features contribute to the imprint of rainfall on deep formation pore pressure. We further modelled pore pressure change due to rainfall based on diffusion mechanism. A strong negative correlation between pore pressure estimated from rainfall and Vs indicates that the Vs variations are triggered by pore pressure diffusion in the deep formation. Our modelling results show a spatial variation of diffusion parameter which controls the pore pressure in deep formation. By linking the variations in seismic velocity and crustal pore pressure spatially, this study shows that seismic monitoring may be useful in evaluating earthquake triggering processes or volcanic activity.
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Posted 06 Nov, 2020
On 24 Nov, 2020
On 06 Nov, 2020
On 29 Oct, 2020
On 29 Oct, 2020
On 29 Oct, 2020
On 23 Oct, 2020
Received 14 Oct, 2020
Received 07 Oct, 2020
On 22 Sep, 2020
On 22 Sep, 2020
On 20 Sep, 2020
Invitations sent on 20 Sep, 2020
On 19 Sep, 2020
On 19 Sep, 2020
On 11 Aug, 2020
Received 29 Jul, 2020
Received 13 Jul, 2020
On 29 Jun, 2020
Invitations sent on 22 Jun, 2020
On 22 Jun, 2020
On 11 Jun, 2020
On 10 Jun, 2020
On 03 Jun, 2020
On 02 Jun, 2020
Spatial and temporal influence of rainfall on crustal pore pressure based on seismic velocity monitoring
Posted 06 Nov, 2020
On 24 Nov, 2020
On 06 Nov, 2020
On 29 Oct, 2020
On 29 Oct, 2020
On 29 Oct, 2020
On 23 Oct, 2020
Received 14 Oct, 2020
Received 07 Oct, 2020
On 22 Sep, 2020
On 22 Sep, 2020
On 20 Sep, 2020
Invitations sent on 20 Sep, 2020
On 19 Sep, 2020
On 19 Sep, 2020
On 11 Aug, 2020
Received 29 Jul, 2020
Received 13 Jul, 2020
On 29 Jun, 2020
Invitations sent on 22 Jun, 2020
On 22 Jun, 2020
On 11 Jun, 2020
On 10 Jun, 2020
On 03 Jun, 2020
On 02 Jun, 2020
Crustal pore pressure, which controls the activities of earthquakes and volcanoes, varies in response to rainfall. The status of pore pressure can be inferred from observed changes in seismic velocity. In this study, we investigate the response of crustal pore pressure to rainfall in southwestern Japan based on time series of seismic velocity derived from ambient noise seismic interferometry. To consider the heterogeneity of the area, rainfall and seismic velocity obtained at each location were directly compared. We used a band-pass filter to distinguish the rainfall variability from sea level and atmospheric pressure, and then calculated the cross-correlation between rainfall and variations in S-wave velocity (Vs). A mostly negative correlation between rainfall and Vs changes indicates groundwater recharge by rainfall, which increases pore pressure. The correlations differ between locations, where most of the observation stations with clear negative cross-correlations were located in areas of granite. On the other hand, we could not observe clear correlations in steep mountain areas, possibly because water flows through river without percolation. This finding suggests that geographical features contribute to the imprint of rainfall on deep formation pore pressure. We further modelled pore pressure change due to rainfall based on diffusion mechanism. A strong negative correlation between pore pressure estimated from rainfall and Vs indicates that the Vs variations are triggered by pore pressure diffusion in the deep formation. Our modelling results show a spatial variation of diffusion parameter which controls the pore pressure in deep formation. By linking the variations in seismic velocity and crustal pore pressure spatially, this study shows that seismic monitoring may be useful in evaluating earthquake triggering processes or volcanic activity.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Due to technical limitations, full-text HTML conversion of this manuscript could not be completed. However, the manuscript can be downloaded and accessed as a PDF.