Seismicity Characterization and Velocity Structure of Northeast Russia

Abstract

Abstract : A seismicity catalog and associated list of phases for many events has been compiled for northeast Russia using published and unpublished data from the regional networks operating in eastern Russia (primarily Magadan, Yakutsk and Amur), and international data files. The catalog contains about 39,000 events and 150,000 arrival times. The resultant catalog is contaminated by industrial explosions, particularly in the Amur and central Magadan districts. A preliminary crustal velocity model was developed by obtaining best fit travel curves in conjunction with locating approximately 1300 events in eastern Russia. The velocities obtained are generally in agreement with inferred tectonic regimes. These travel time curves were then used to relocate 134 larger regional events; 26 are classified as GT10. From these relocated events consistent patterns of residuals, essentially representing Source Specific Station Corrections (SSSCs), show upper mantle velocities are elevated under the Siberian platform and slower below the Sea of Okhotsk. Seismic station parameters for the region were also compiled. To further improve calibration capabilities in northeast Russia, a small network of digital seismic stations was deployed in the Magadan region, recording both earthquakes and ground truth mine blasts. Preliminary analysis of Lg amplitude ratios indicate that the ratio Lg(4-8Hz)Lg(0.75-1.5Hz) using peak amplitudes is not sufficient to discriminate mining explosions from earthquakes at local and near regional distances (<500km) in northeast Russia.