Seismic characterisation of lahars at Volcán de Co

Authors: R Vázquez E Suriñach L Capra R ArámbulaMendoza G ReyesDávila

Publish Date: 2016/02/09

Volume: 78, Issue: 2, Pages: 8-

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Abstract

Volcán de Colima is one of the most active volcanoes in Mexico not only for its eruptive history but also for its annual occurrence of lahars This makes the volcano a natural laboratory for monitoring and studying lahar processes Since 2011 monitoring instruments have been deployed along the highly active Montegrande ravine with at least three lahar events per year Here we report the datasets of three events collected during the 2012 and 2013 seasons then interpret the acquired data An event classification scheme based on lahar magnitude duration and seismic characteristics is presented to distinguish “singlepulse” events SPEs from “multipulse” events MPE SPEs lasted approximately 60 min had average velocities of ~2 m/s and mean peak discharges of ~24 m3/s MPEs endured for more than 3 h reached mean velocities of ~45 m/s and peak discharges of ~60 m3/s for blockrich surges The seismic signalanalysis also allowed us to discriminate physical flow fluctuations within single lahars ie between the arrival of blockrich fronts and subsequent variations in flow discharge The exponential regression analysis showed a best fit with correlation coefficients around 092 and exponential coefficients of ~001 s for the blockrich fronts with seismic amplitudes increasing from 48 × 10−4 to 23 × 10−3 m/s and frequency ranges from 10 to 20 Hz The variations in flow discharge were distinguished by lower amplitudes of ~57 × 10−4 m/s than those of the blockrich fronts and with frequency ranges of 10–40 Hz The results presented in this paper demonstrate that the seismic data of events allowed us to describe and discriminate among different flow types these records are thus a useful investigation tool for lahar events that have a seismic record but are not observed directly We propose that a seismic early warning system can be developed to help civil protection authorities in designing risk mitigation strategiesThis work was supported by the CONACyT 99486 PAPIITUNAM IN106710 and SRECONACyT 146324 projects to Lucia Capra The Spanish MINECO project CGL201340828R partially supported this investigation Thanks to the staff of Centro Nacional de Prevención de Desastres CENAPRED for the instrumentation setup in the Montegrande monitoring site Thanks to Penélope López for managing the Spot image acquisition from ERMEXSPOT IMAGE SA The first author spent 6 months in the Departament de Geodinàmica i Geofísica at Universitat de Barcelona and wish to thank them for the support during that time Special thanks to the associate editor Gert Lube for handling this paper and the two anonymous reviewers for insightful comments that greatly improved this work

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