Tectonic Setting and Aftershocks of the Mw 6.7 Feburary 14, 2013 Earthquake in Yakutia, Northeast Russia

The details of the seismotectonics along the boundary between the Eurasian, North American, and Okhotsk plates are poorly understood. Infrequent earthquakes of moderate size (Mw > 4) in this remote region make it difficult to characterize its tectonic activity. On February 14, 2013, an Mw 6.7 earthquake along this boundary in Northern Yakutia, Russia, resulted in a long sequence of aftershocks that provide an opportunity to better understand the region's geology. A temporary deployment of four seismic stations was installed around the main shock to supplement regional station coverage. During the ten day deployment, several thousand aftershocks were recorded. We have located 112 events using both first-arriving Pn and Sn and secondary arriving Pg and Sg phase time picks. The located aftershocks define a SSE striking zone approximately 30 km long and 10 km wide, east of the Illin'-Tas fault and northwest of the Indigirka River. Location depths range from 0 to 20 km. In conjunction with locating aftershocks, a local three-layer best-fit velocity was determined consisting of an upper crust (14 km thick, VPg = 6.06 km/s and VSg = 3.53 km/s), a lower crust (21 km thick, VP* = 6.45 km/s and VS* = 3.65 km/s), and a Moho (35 km deep, VPn = 7.98 km/s and VSn = 4.53 km/s). The mainshock epicenter falls in the northwestern corner of the aftershock zone, however its focal depth is not well established. Aftershock analysis is ongoing and will possibly provide a better understanding of the earthquake rupture zone. Nonetheless, results of this study support active thrusting and mountain building as a mechanism to accommodate compression along the North America-Eurasia boundary.