| The Artyk earthquake of May 18, 1971, is the largest earthquake in continental northeast Russia in the instrumental era. An extensive aftershock sequence occurred during the three months following the mainshock. 286 of these events were relocated using an expanded data set incorporating data from both temporary and regional stations, and using a local travel-time curve.;The relocated aftershocks align very closely with the Kobdi fault as mapped by Shilo (1961) and form two clusters. The northern cluster has the same strike as the northwest-striking nodal plane of the focal mechanism, indicating left-lateral strike-slip movement. The southern cluster shows a bend to the east. The Kobdi fault appears to offset a diorite by about 8 km, yielding an inferred rate of motion of 0.2 cm/yr on the fault.;The left-lateral strike-slip nature of the mainshock, the northwest-striking aftershock distribution, and the lack of faults with a southwest or east to northeast strike, and recent activity on the Ulakhan fault to the northeast imply the earthquake cannot lie on the North America -- Okhotsk or Okhotsk -- Eurasia plate boundaries or at a triple junction between them. Instead, the Artyk earthquake was generated along a fault that represents internal deformation in the Okhotsk plate. |
