Seismic Observations of the 15 February 2013 Chelyabinsk Meteor from Dense ChinArray

Abstract:

Since the 1908 Tunguska event, the largest meteor was reported on 15 February 2013 around 03:20:00 UTC. The fireball exploded and dropped near Chelyabinsk, Russia. Massive energy released by meteor crash was recorded by the 500-station ChinArray deployed in southwest China at distances more than 4000 kilometers from the meteor event. About 20 minutes before the meteor event, an M5.8 event occurred in Tonga, and produced seismic waves that overlapped with the seismic signals from the meteor event. Here we separate the seismic phases from the two events using standard array processing techniques such as F-K analysis, beam-forming, and vespagram in the Generic Array Processing (GAP) code (Koper, 2005). F-K analysis provides an effective way to calculate the back azimuth and slowness of a seismic phase. With this method, we identify a phase with back azimuth of 339.1°and slowness of 37.46sec/deg as surface wave from meteor. Beam-forming technique can be used to amplify the signal of meteor generated surface wave and suppress incoherent noise and phases with different slowness from the Tonga event. Vespagram shows the appropriate slowness of ~35sec/deg at arrival of meteor’s phase, confirming the F-K detection of surface wave. From the surface wave observation, we conclude that the seismic source of meteor is located on 61.39N 58.70E, which is ~700km away from the USGS location (55.15N 61.41E). Using the Praha relation [Karnik et al., 1962], we estimate a magnitude of Ms=3.94±0.18 in accordance with that of Ms~3.7 [Benoit Tauzin et al., 2013]. Our result is comparable to other observations with shorter epicentral distances, suggesting that dense seismic arrays can be used to detect weak seismic signals at long-range distances.