3D Seismic Reflection Imaging with Microearthquakes using Large N Arrays

Larry Brown*1, Doyeon Kim, Diego Quiros2

1Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY, USA (ldb7@cornell.edu). 2Department of Geosciences, Baylor University, Waco Texas, 76798

Reflection seismology with controlled sources often provides the highest resolution of structure of any seismic technique. However, the application of the reflection method to probe all but the shallowest of structures is often inhibited by the substantial cost of artificial sources as well as logistical barriers to their deployment. Here we describe how reflection processing can be applied to recordings of microearthquakes to produce reflection imagery that approaches the quality of conventional controlled source (CMP) surveys. Such “passive” seismic reflection imaging has only recently become practical with the advent of large N nodal technology that can simultaneously record spatially dense arrays for substantial lengths of time.  Two distinct approaches will be described: seismic interferometry to  re-datum microearthquakes into virtual surface sources and reverse VSP imaging of microearthquakes. Examples from Iceland, the eastern US and Alaska suggest that these methods represent a transformative approach to imaging deep structure and monitoring active processes in areas illuminated by transient or ongoing microseismicity.