Global variations of stress drop for moderate to large earthquakes
Global variations of stress drop for moderate to large earthquakes
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DOI：
10.1029/2008jb005821
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发表时间：
2009-01-23
影响因子：
3.9
通讯作者：
Shearer, Peter M.
中科院分区：
文献类型：
--
作者：
Allmann, Bettina P.;Shearer, Peter M.
我们使用1990年至2007年之间约2000个m（B）≥ 5.5的地震事件的谱来研究地震应力降的全球变化。我们使用迭代最小二乘法分离源位移谱从旅行路径和接收器的贡献，基于卷积模型。用全局平均的经验校正谱和近源衰减估计对观测到的P波源谱进行了校正。假设一个Brune型源模型，我们估计拐角频率和计算应力降。单个地震的应力降估计值范围约为0.3至50 MPa，但约4 MPa的中值应力降不随力矩而变化，这意味着我们的数据在M-W = 5.2至8.3范围内存在地震自相似性。我们的结果与以前的研究比较证实了这一观察在大多数仪器可观测的星等范围。虽然我们估计的应力降的绝对值取决于假设的源模型，我们确定的相对区域变化的应力降是强大的处理参数和建模假设，其中包括一个固有的假设恒定的破裂速度。我们发现，中值应力降的震源机制的依赖性，与3-5倍高的应力降的因素为走滑地震，也发现了2倍高的应力降的因素为板内地震相比，板间地震。
We investigate the global variation of earthquake stress drops using spectra of about 2000 events of m(b) >= 5.5 between 1990 and 2007. We use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions, based on a convolutional model. The observed P wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near-source attenuation. Assuming a Brune-type source model, we estimate corner frequencies and compute stress drops. Stress drop estimates for individual earthquakes range from about 0.3 to 50 MPa, but the median stress drop of about 4 MPa does not vary with moment, implying earthquake self-similarity over the M-w = 5.2 to 8.3 range of our data. A comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range. While the absolute values of our estimated stress drops depend upon the assumed source model, we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions, which includes an inherent assumption of constant rupture velocity. We find a dependence of median stress drop on focal mechanism, with a factor of 3-5 times higher stress drops for strike-slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes.