TY  - JOUR
A1  - Illien, Luc
A1  - Sens-Schönfelder, Christoph
A1  - Andermann, Christoff
A1  - Marc, Odin
A1  - Cook, Kristen L.
A1  - Adhikari, Lok Bijaya
A1  - Hovius, Niels
T1  - Seismic velocity recovery in the subsurface
T2  - Journal of geophysical research : Solid earth
N2  - Shallow earthquakes frequently disturb the hydrological and mechanical state of the subsurface, with consequences for hazard and water management. Transient post-seismic hydrological behavior has been widely reported, suggesting that the recovery of material properties (relaxation) following ground shaking may impact groundwater fluctuations. However, the monitoring of seismic velocity variations associated with earthquake damage and hydrological variations are often done assuming that both effects are independent. In a field site prone to highly variable hydrological conditions, we disentangle the different forcing of the relative seismic velocity variations delta v retrieved from a small dense seismic array in Nepal in the aftermath of the 2015 M-w 7.8 Gorkha earthquake. We successfully model transient damage effects by introducing a universal relaxation function that contains a unique maximum relaxation timescale for the main shock and the aftershocks, independent of the ground shaking levels. Next, we remove the modeled velocity from the raw data and test whether the corresponding residuals agree with a background hydrological behavior we inferred from a previously calibrated groundwater model. The fitting of the delta v data with this model is improved when we introduce transient hydrological properties in the phase immediately following the main shock. This transient behavior, interpreted as an enhanced permeability in the shallow subsurface, lasts for similar to 6 months and is shorter than the damage relaxation (similar to 1 yr). Thus, we demonstrate the capability of seismic interferometry to deconvolve transient hydrological properties after earthquakes from non-linear mechanical recovery.
KW  - earthquake damage
KW  - earthquake hydrology
KW  - relaxation
KW  - Gorkha earthquake
KW  - seismic monitoring
KW  - ambient noise
Y1  - 2022
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/63732
SN  - 2169-9313
SN  - 2169-9356
VL  - 127
IS  - 2
PB  - American Geophysical Union
CY  - Washington
ER  -