HR: 1330h
AN: S42E-0214    [PDF]
TI: Aftershock Study of the 2003 Armeria, Colima, Mexico, Earthquake (Mw = 7.4).
AU: * Nunez-Cornu, F J
EM: fcornu@pv.udg.mx
AF: Centro de Sismologia Volcanologia de Occidente, Univ. de Guadalajara, Av. Universidad 203, Del. Ixtapa, Puerto Vallarta, Jal 48280 Mexico
AU: Reyes-Davila, G A
EM: gard@cgic.ucol.mx
AF: RESCO, Universidad de Colima, Av. 25 de Julio 602, Colima, Col 28045 Mexico
AU: Rutz Lopez, M
AF: Centro de Sismologia Volcanologia de Occidente, Univ. de Guadalajara, Av. Universidad 203, Del. Ixtapa, Puerto Vallarta, Jal 48280 Mexico
AU: Marquez-Ramirez, V
AF: RESCO, Universidad de Colima, Av. 25 de Julio 602, Colima, Col 28045 Mexico
AU: Trejo Gomez, E
AF: Centro de Sismologia Volcanologia de Occidente, Univ. de Guadalajara, Av. Universidad 203, Del. Ixtapa, Puerto Vallarta, Jal 48280 Mexico
AU: Camarena Garcia, M
AF: Centro de Sismologia Volcanologia de Occidente, Univ. de Guadalajara, Av. Universidad 203, Del. Ixtapa, Puerto Vallarta, Jal 48280 Mexico
AU: Ramirez-Vazquez, C A
AF: RESCO, Universidad de Colima, Av. 25 de Julio 602, Colima, Col 28045 Mexico
AU: Suarez-Plascencia, C
EM: csuarez@cencar.udg.mx
AF: Centro de Sismologia Volcanologia de Occidente, Univ. de Guadalajara, Av. Universidad 203, Del. Ixtapa, Puerto Vallarta, Jal 48280 Mexico
AB: On January 22, 2003 an earthquake (Mw7.4) took place in the southeastern limit of the Jalisco Block(JB) offshore of the town of Armeria, Colima; an area aside of where a great shallow thrust earthquake (Mw8.0) occurred in 1995 and has been proposed as a seismic gap. We analyze two aftershocks periods, the first 72 hours after the main shock (MS) using data from the two permanent local networks in the region (RESCO and RESJAL). The second period, from 25 to 31 January, when seven portable digital triaxial stations were deployed at the epicentral area. Analysis from first period data shows epicentral distribution of aftershocks in two small clusters, one around and north of the MS and the second on the 1995 Earthquake epicentral area. Hypocenters are very shallow (between 2 and 10 km depth) in a distribution almost vertical, this suggest an early aftershock area roughly rectangular, about 42 x 25 km, and dipping about $40\deg$ in an almost EW direction, located at 70 km NE of the trench axis; assumed to correspond to the rupture area. The focal mechanism for the MS agrees with these data. For the second period epicentral distribution is similar to MS cluster, however a migration in depth is observed, most of the hypocenters are at a depth between 14 and 24 km, and seems to be distributed along the interphase between JB and Rivera Plate assuming a $12\deg$ dipping. Our results indicate that the Earthquake was a continental intraplate inverse fault event. These data do not support the possible rupture of the Colima Gap.
DE: 7205 Continental crust (1242)
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 8105 Continental margins and sedimentary basins
DE: 8123 Dynamics, seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting