The rotational and gravitational signature of the December 26, 2004 Sumatran earthquake
The rotational and gravitational signature of the December 26, 2004 Sumatran earthquake
复制标题
DOI：
10.1007/s10712-006-9008-1
复制
发表时间：
2006-08
影响因子：
4.6
通讯作者：
R. Gross;B. Chao
中科院分区：
文献类型：
--
作者：
R. Gross;B. Chao
除了产生最终消散的地震波外，地震还在地球内部的任何地方产生静态位移场。这种全球位移场重新排列地球的质量，从而导致地球的自转和引力场发生变化。这种变化的大小取决于震级、震源机制和地震的位置。2004年12月26日发生的苏门答腊地震是自1960年智利地震以来发生的最大地震。利用球形分层地球模型，计算了Summerian地震对地球日长、极移和引力场低阶谐波系数的同震效应。用一个由五个总矩震级Mw为9.3的子事件组成的震源模型，发现这次地震应使日长减少6.8微秒，地球广义形状轴的位置向东经127°移动2.32毫角秒，地球的扁率J2将减少2.37 × 10− 11，而地球的梨形J3将减少0.63 × 10−11。预测的日长、广义图轴位置和J3的变化可能无法通过当前的测量系统检测到。但是，如果其他影响，如大气、海洋和大陆水储存的影响，可以从观测中充分去除，那么预测的扁率变化也许是可以检测到的。
Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth’s mass thereby causing the Earth’s rotation and gravitational field to change. The size of this change depends upon the magnitude, focal mechanism, and location of the earthquake. The Sumatran earthquake of December 26, 2004 is the largest earthquake to have occurred since the 1960 Chilean earthquake. Using a spherical, layered Earth model, the coseismic effect of the Sumatran earthquake upon the Earth’s length-of-day, polar motion, and low-degree harmonic coefficients of the gravitational field are computed. Using a model of the earthquake source that is composed of five subevents having a total moment-magnitudeMwof 9.3, it is found that this earthquake should have caused the length-of-day to decrease by 6.8 microseconds, the position of the Earth’s generalized figure axis to shift 2.32 milliarcseconds towards 127° E longitude, the Earth’s oblatenessJ2to decrease by 2.37 × 10−11and the Earth’s pear-shapednessJ3to decrease by 0.63 × 10−11. The predicted change in the length-of-day, position of the generalized figure axis, andJ3are probably not detectable by current measurement systems. But the predicted change in oblateness is perhaps detectable if other effects, such as those of the atmosphere, oceans, and continental water storage, can be adequately removed from the observations.