Role of S waves and Love waves in coseismic permeability enhancement

Abstract

The 2008 M7.9 Wenchuan earthquake in Sichuan, China, caused water level to oscillate and undergo sustained changes in Taiwan, ∼2000 km away from the epicenter. Here we use the responses in three wells recorded at high sampling rate (1 Hz) and the broadband seismograms from a nearby station to document, for the first time, that the major water-level responses associated with Rayleigh waves were preceded by small oscillations that occurred concurrently with S waves and Love waves. We also show that the groundwater flow associated with these small oscillations may be strong enough to remove blockades from sediment pores to enhance aquifer permeability and to facilitate the later major responses. Copyright 2009 by the American Geophysical Union.