The fracturing in volcanic edifice before an eruption; the June-July 1998 high-frequency earthquake swarm at Volcán de Colima, México

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doi: 10.1016/S0377-0273(00)00243-2
Authors:Domínguez, T.; Zobin, V. M.; Reyes-Dávila, G. A.
Author Affiliations:Primary:
Universidad de Colima, Centro Universitario de Investigacion en Ciencias del Ambiente, Colima, Mexico
Volume Title:Journal of Volcanology and Geothermal Research
Source:Journal of Volcanology and Geothermal Research, 105(1-2), p.65-75. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-0273
Publication Date:2001
Note:In English. 15 refs.; illus., incl. 1 table, geol. sketch maps
Summary:The recent eruption of Volcan de Colima, Mexico, began in November 1998 and was preceded by a 12-month period of seismic activity, which consisted from a few swarms of numerous microeathquakes. We study the source characteristics of earthquakes that occurred during June-July, 1998, swarm within the edifice of Volcan de Colima, which consists of the dormant Nevado de Colima and active Volcan de Fuego. A three-component digital seismic station, added to the one-component seismic network of five stations during this period, allowed us to analyze S-wave spectra for our study. Thirty-two microearthquakes with hypocentral distances up to 7 km and magnitudes Mw between 0.5 and 1.8 were analyzed in the frame of Brune's model. These events were characterized by high-frequency radiation with corner frequencies from 3.9 to 9.0 Hz. Their seismic moments varied from 0.9×1010 to 7.2×1011 N-m and stress drops were obtained in the range between 0.05 and 13 bars. We found three groups of events with different corner frequencies that may reflect the presence of three fracture zones with distinct characteristic lengths of fissures formed by the subsurface dike intrusion before the eruption. The first stage (from June 16 to July 3) of swarm development was characterized by simultaneous fracturing within two fracture zones. The first zone was represented by a system of fractures with length of about 80-90 m and was situated below Nevada de Colima, the second zone was represented by a system of fractures with length of about 130-150 m and was situated below the crater zone of Volcan de Fuego. The second stage (from July 4 to 6) of swarm development was characterized by simultaneous fracturing within three fracture zones. A third zone was added to the first two zones with the fracture length of intermediate size about 110 m. The majority of foci that occurred from June 16 to July 3 were situated along the SE slope of Nevado de Colima; the events of July 4 to 6 occurred mainly below the crater zone of Volcan de Fuego. The fracturing in the volcanic edifice occurred within a system of fractures of ENE direction tracing by epicenters and coinciding with the general trend of Tamazula regional fault that intersects the volcanic structure. We suggested that this development of the earthquake swarm reflects either (1) the migration of dike to the active crater of Volcan de Colima or (2) the growth of branches of the dike-swarm tree within the volcanic edifice. Abstract Copyright (2001) Elsevier, B.V.
Sections:Petrology
Subsections:Volcanology
Subjects:Deformation; Dikes; Earthquakes; Eruptions; Faults; Focal mechanism; Induced earthquakes; Intrusions; Microearthquakes; Seismic moment; Seismicity; Spatial distribution; Stress; Swarms; Volcanic earthquakes; Volcanism; Volcanoes; Colima; Jalisco Mexico; Mexico
Coordinates:N193100 N193100 W1033800 W1033800
Abstract Numbers:01M/4623
Record ID:2001022831
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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