Open AccessA mechanism for sustained groundwater pressure changes induced by distant earthquakes
Author(s) -
Brodsky Emily E.,
Roeloffs Evelyn,
Woodcock Douglas,
Gall Ivan,
Manga Michael
Publication year - 2003
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002jb002321
Subject(s) - geology , induced seismicity , groundwater , pore water pressure , seismology , hydrothermal circulation , amplitude , water level , groundwater flow , aquifer , geotechnical engineering , physics , cartography , quantum mechanics , geography
Large, sustained well water level changes (>10 cm) in response to distant (more than hundreds of kilometers) earthquakes have proven enigmatic for over 30 years. Here we use high sampling rates at a well near Grants Pass, Oregon, to perform the first simultaneous analysis of both the dynamic response of water level and sustained changes, or steps. We observe a factor of 40 increase in the ratio of water level amplitude to seismic wave ground velocity during a sudden coseismic step. On the basis of this observation we propose a new model for coseismic pore pressure steps in which a temporary barrier deposited by groundwater flow is entrained and removed by the more rapid flow induced by the seismic waves. In hydrothermal areas, this mechanism could lead to 4 × 10 −2 MPa pressure changes and triggered seismicity.