A deep earthquake aftershock sequence and implications for the rupture mechanism of deep earthquakes
A deep earthquake aftershock sequence and implications for the rupture mechanism of deep earthquakes
复制标题
深部地震余震序列及其对深部地震破裂机制的影响
作者：
D. Wiens;J. McGuire;P. Shore;M. Bevis;K. Draunidalo;G. Prasad;S. Helu
深源地震的一个显著特点是没有可观测到的余震序列1，2。在这里，我们报告的第一个广泛的深地震余震序列进行观察，它是由一个阵列的8个宽带地震仪记录在1994年3月9日深汤加地震。余震在主震之后随时间呈幂律衰减，这是典型的浅层地震。大多数定位良好的余震都集中在沿着一个陡峭的倾斜面，与主震机制和三个大余震机制的节面之一一致。假设这些余震代表主震破裂区，那么它们就定义了一个50 × 65 km的断层面，该断层面横跨活动地震带的整个宽度，并延伸到周围的无震区。余震区的宽度比亚稳橄榄石楔的预期宽度要宽，这表明亚稳橄榄石材料的宽度超过了以前的估计，或者余震没有被限制在这样的楔中。
A distinguishing characteristic of deep earthquakes has been the absence of observable aftershock sequences1,2. Here we report the first extensive deep-earthquake aftershock sequence to be observed; it was recorded by an array of eight broadband seismographs following the 9 March 1994 deep Tonga earthquake. The aftershocks show a power-law decay with time following the main shock, as is typical of shallow events. Most of the well located aftershocks are concentrated along a steeply dipping plane consistent with one of the nodal planes of the main-shock mechanism and the mechanisms of three large aftershocks. Assuming these aftershocks denote the main-shock rupture area, they define a 50 × 65 km fault plane extending across the entire width of the active seismic zone and into the surrounding aseismic region. The width of the aftershock zone is wider than the expected width of the metastable olivine wedge, demonstrating that either the width of the metastable olivine material exceeds previous estimates, or the aftershocks are not confined in such a wedge.