Characterization of the October microearthquake swarm in the Socorro region

Abstract

Socorro, New Mexico lies in a region of increased seismicity caused by a mid-crustal magma body. The magma body is at about 19 km depth beneath central NM, and has an area of approximately 3000 km 2 . On October 30, 2005 at 02:57:35 (UTC), many residents of the city of Socorro felt an earthquake of magnitude 2.4. Although events of such magnitude are rarely felt, this earthquake was very close to the city’s population center. The earthquake’s epicenter was located at 34.06N and 106.96W, or approximately 5.4 km west of the city. The depth to the hypocenter was about 7 km. Subsequently, seismic activity increased in the region of the main shock. On the day of the main event, over 200 microearthquakes occurred. In the period between October 30 and November 17, 2005, many microearthquakes occurred with numbers decreasing exponentially in time. Here we describe the location of these events, present analyses of their waveform similarity, and compare with previous microearthquake swarms in this area. These microearthquakes seem to have very similar waveforms to the main event, which suggests that they occurred in close proximity to the main event. This earthquake swarm appears to be similar to the previous swarms in May and July 1983, with earthquakes occurring in approximately the same location.