Resumo

VALENZUELA, Raúl W. et al. The seismic and hydroacoustic stations on Socorro Island: Early results. Geofís. Intl [online]. 2007, vol.46, n.1, pp. 3-18. ISSN 0016-7169.

A seismic and hydroacoustic network on Socorro Island was installed jointly by the Servicio Sismológico Nacional, Instituto de Geofísica, Universidad Nacional Autónoma de México, and the Comprehensive Nuclear-Test-Ban Treaty Organization. The detection of ten earthquakes in June and July 2004 is reported in this study. These events occurred at epicentral distances between 209 and 9050 km and ranged in magnitude between 3.9 and 6.8. An event in the Kamchatka Peninsula featured arrivals of teleseismic high-frequency P and pP waves from a distance of 8245 km. An earthquake in the Guerrero-Oaxaca, Mexico, region shows clear seismic and T phases. Three earthquakes in the Rivera Fracture Zone were recorded, thus leading to the expectation of the continued detection of events from nearby fracture zones as well as earthquakes generated by volcanoes on Socorro and San Benedicto Islands. The analysis of the T phases from several events validates the design of the network, with three sites around the island in order to record arrivals from all directions. High frequency seismic waves generated by acoustic waves attenuate as they propagate through the rock from one end of the island to the other. Consequently small or distant events are difficult to detect at the far side of the island.

Palavras-chave : Comprehensive Nuclear-Test-Ban Treaty (CTBT); Sound Fixing and Ranging (SOFAR) channel; nuclear explosions; Socorro Island; T phases, Rivera Fracture Zone; Pacific ocean.