Relocalization and Focal Mechanisms of Volcano-Tectonic Events at Colima Volcano, Colima, Mexico
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Pure and Applied Geophysics
Relocalization and Focal Mechanisms of Volcano-Tectonic Events at Colima Volcano, Colima, Mexico ARACELI ZAMORA-CAMACHO,1
JUAN MANUEL ESPINDOLA,2 QUIRIAT J. GUTIE´RREZ-PEN˜A,3 and LUIS QUINTANAR2
Abstract—Colima volcano (19.51 N, 103.62 W, 3860 m.a.s.l.) in western Mexico is well known for its frequent activity. Along with nearby Nevado de Colima, and Ca´ntaro volcanoes are part of a volcanic complex rising in the middle of the Colima graben, a structure on the margin of the Jalisco Block, some one hundred km from the Middle America trench. The activity of Colima volcano is varied and usually accompanied by intense seismicity, mostly of volcano-tectonic events. To investigate several aspects of these earthquakes, we analyzed events recorded by the seismological network of Colima during the outbursts of 1998–1999, 2005, and 2009. Those periods, of varying intensity, lasted from several months to several weeks before and after a significant explosive event. The hypocenters, located with standard methods, appear in a broad region around the volcanic complex. To obtain a more accurate location of these events, we relocated the hypocenters using the method of double differences. A set of 1191 relocated events was obtained, providing improved locations, which show hypocenters clustered under the edifice of Colima volcano and do not seem to be related to any particular geological feature and, therefore, represent the volume stressed by magma’s intrusion. The focal mechanism of the relocated events shows a variety of fault plane orientations with a majority indicating dip-slip faulting. Keywords: Colima volcano, volcano seismicity, Colima volcano complex, volcanic earthquake swarms, volcano-tectonic earthquakes.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00024-020-02540-x) contains supplementary material, which is available to authorized users. 1
Departamento de Ciencias Exactas, Centro Universitario de la Costa, Universidad de Guadalajara, Av. Universidad 203, C.P. 48280 Puerto Vallarta, Mexico. E-mail: [email protected] 2 Instituto de Geofı´sica, Universidad Nacional Auto´noma de Me´xico, Ciudad Universitaria, Coyoaca´n, C.P. 04510 Ciudad de Me´xico, Mexico. 3 Posgrado en Ciencias de la Tierra, Centro de Investigacio´n Cientı´fica y de Educacio´n Superior de Ensenada, Carretera Ensenada-Tijuana No. 3918, Zona Playitas, C.P. 22860 Ensenada, BC, Mexico.
1. Introduction Colima volcano (aka as Volca´n de Colima and Volca´n del Fuego) in western Mexico (19.51 N, 103.62 W, 3860 masl), the most active volcano in the country, experiences frequent eruptions of diverse style (Fig. 1a). Its last intense explosive eruption took place in 1913 (VEI = 5) and has remained after that in a state of unrest, which in the last decades has been characterized by episodes of dome construction and destruction through great explosions. In the last decades, events of this type have occurred in 1991, 1998–1999, 2001, 2005, 2013, 2014, 2015, 2016, and January 20
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