A high-frequency secondary event during the 2004 Parkfield earthquake

被引:55
作者
Allmann, Bettina P. [1 ]
Shearer, Peter M. [1 ]
机构
[1] Univ Calif San Diego, Scripps Inst Oceanog, Cecil H & Ida M Green Inst Geophys & Planetary Ph, La Jolla, CA 92093 USA
关键词
D O I
10.1126/science.1146537
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
By using seismic records of the 2004 magnitude 6.0 Parkfield earthquake, we identified a burst of high-frequency seismic radiation that occurred about 13 kilometers northwest of the hypocenter and 5 seconds after rupture initiation. We imaged this event in three dimensions by using a waveform back-projection method, as well as by timing distinct arrivals visible on many of the seismograms. The high-frequency event is located near the south edge of a large slip patch seen in most seismic and geodetic inversions, indicating that slip may have grown abruptly at this point. The time history obtained from full-waveform back projection suggests a rupture velocity of 2.5 kilometers per second. Energy estimates for the subevent, together with long-period slip inversions, indicate a lower average stress drop for the northern part of the Parkfield earthquake compared with that for the region near its hypocenter, which is in agreement with stress-drop estimates obtained from small-magnitude aftershocks.
引用
收藏
页码:1279 / 1283
页数:5
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