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Travel‐time tomography in the northern Coachella Valley using aftershocks of the 1986 M L 5.9 North Palm Springs Earthquake
Author(s) -
Nicholson Craig,
Lees Jonathan M.
Publication year - 1992
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/91gl03037
Subject(s) - aftershock , geology , seismology , asperity (geotechnical engineering) , inversion (geology) , fault (geology) , arrival time , anomaly (physics) , seismic velocity , seismic tomography , tectonics , geophysics , mantle (geology) , geotechnical engineering , condensed matter physics , transport engineering , engineering , physics
Tomographic inversion is applied to delay times from aftershocks of the 1986 M L 5.9 North Palm Springs (NPS) earthquake to image 3‐D velocity variations within the northern Coachella Valley. P‐wave arrival times from 1074 earthquakes, with depths ranging from 3 to 20 km, were used as sources recorded by 12 portable and 4 permanent stations. Preliminary results show well‐defined high‐ and low‐velocity anomalies (2–7%) that correlate with the rupture distribution of the 1986 mainshock. At depths less than 8 km, a low‐velocity anomaly predominates between the two NE‐dipping Banning and Mission Creek faults. From 8 to 12 km in depth, where the NPS mainshock and most of the aftershocks occur, a high‐velocity anomaly is observed. This high‐velocity feature is interpreted as imaging the asperity responsible for the 1986 rupture; and suggests that velocity information may help to define important elements, such as asperities, that control fault rupture, and thus, may help to predict the location and size of future events.