Collaborative Research:Aftershock Imaging with Dense Arrays (AIDA) for the August 23, 2011, Mw 5.8, Virginia earthquake aftershock sequence

利用IRIS/PASSCAL提供的Earthscope柔性阵列设备，RAPID支持新型高密度地震阵列的震后部署，以调查2011年8月23日发生在弗吉尼亚的5.8级地震。这次地震的震源机制为北东向逆断层，震源深度为6公里（美国地质调查局），发生在先前被认为是中弗吉尼亚地震带的地震区。1981年，美国地质调查局（USGS）收集了一条大约15公里的北西-东南方向的深部地震反射剖面，这为将地震活动与美国东部的深部结构联系起来提供了难得的机会。初步的震源估计表明，地震发生在一个东倾反射的复杂区域，该区域界定了阿巴拉契亚山前山中部的一个叠瓦状古生代逆冲板，该板位于格伦维尔基底之下，深度约为9公里。通过将地震定位技术与高分辨率结构成像技术相结合，本实验旨在展示如何利用被动地震和主动地震技术来识别深层发震结构，以及在这两种信息都很少或不存在的地区识别能量传播特征。该记录实验是利用新一代记录技术以前所未有的分辨率成像地震过程和相关结构的原型。如果数据像预期的那样丰富，这个实验很可能为未来的余震研究建立一个新的方案。

This RAPID supports post-seismic deployment of novel high density seismic arrays using instruments from the Earthscope Flexible Array provided by IRIS/PASSCAL to investigate the Mw 5.8 Virginia earthquake of August 23, 2011. This event had a NE-striking reverse faulting focal mechanism, a hypocentral depth of 6 km (USGS), and occurred in a previously recognized seismic region known as the Central Virginia Seismic Zone. This event passes with ca. 15 km of a NW-SE oriented deep seismic reflection profile contracted in 1981 by the USGS, providing a rare opportunity to link seismicity to deep structure in the eastern U.S. The preliminary hypocentral estimate suggests that the earthquake occurred within a complex zone of east-dipping reflections that define an imbricated Paleozoic thrust sheet of the central Appalachian Piedmont that is underlain by Grenville basement at a depth of ca. 9 km.By merging the technologies of earthquake location with high resolution structural imaging, this experiment seeks to demonstrate how aftershocks can be exploited by both passive and active seismic techniques to identify seismogenic structures at depth as well as energy propagation characteristics for a region where both types of information are either rare or non-existent. The recording experiment constitutes a prototype for imaging earthquake processes and associated structures with unprecedented resolution by exploiting a new generation recording technologies. If the data proves as rich as expected, this experiment may well establish a new protocol for future aftershocks studies.