CaltechAUTHORS
  A Caltech Library Service

Stress tensor analysis of the 1998–1999 tectonic swarm of northern Quito related to the volcanic swarm of Guagua Pichincha volcano, Ecuador

Legrand, D. and Calahorrano, A. and Guillier, B. and Rivera, L. and Ruiz, M. and Villagómez, D. and Yepes, H. (2002) Stress tensor analysis of the 1998–1999 tectonic swarm of northern Quito related to the volcanic swarm of Guagua Pichincha volcano, Ecuador. Tectonophysics, 344 (1-2). pp. 15-36. ISSN 0040-1951. https://resolver.caltech.edu/CaltechAUTHORS:20171128-132156892

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20171128-132156892

Abstract

The phreatic activity and the subsequent dacitic dome growth in 1998–1999 at Guagua Pichincha volcano, Ecuador, were associated with two seismic swarms: one located in the northern part of Quito (population: 1,500,000) and another one, just below the active volcano, about 15–20 km SW from the first one. Quito swarm tectonic events have high frequencies (from 1 to 10–15 Hz). We registered more than 3200 events (among which 2354 events of 1.4≤M_L≤4.2) between June 1998 and December 1999 at the −2- and −17-km depth. The volcanic events below the Guagua Pichincha caldera have high (from 1 to 10–15 Hz) and low (less than 3 Hz) frequencies. Approximately, 130,000 events were registered between September 1998 and December 1999 at the +2.4- and −3.5-km depth. Here, we study the stress tensors of these two swarms deduced from the polarities of P first motions and compare them to the regional stress tensor deduced from CMT Harvard focal mechanisms. The Quito swarm stress tensor is relatively close to the regional stress tensor (the σ_1 axis was oriented N117°E close to the N102°E direction of the plate motion found by the GPS measurement, and σ_3 is nearly vertical). The difference may be due to the action of the closely active Guagua Pichincha volcano. The Guagua Pichincha stress tensor is very different from the regional tectonic one. The σ_1 axis of the volcano is oriented N214°E, almost perpendicular to the σ_1 of the swarm of Quito and σ_3 is almost horizontal. Even if these two tensors are different, they can be explained in a more general tectonic scheme. The almost horizontal direction of σ_3 just below the volcano is compatible with an extensional horizontal direction that may be expected in the shallow extrados part of a compressional region and consistent with an opening of the top of the Guagua Pichincha volcano. The movement of the fluids (magma, gas and/or groundwater) produced by the closely active Guagua Pichincha volcano seems to have an influence in the acceleration of the generation of seismic events.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/S0040-1951(01)00273-6DOIArticle
http://www.sciencedirect.com/science/article/pii/S0040195101002736PublisherArticle
ORCID:
AuthorORCID
Rivera, L.0000-0002-0726-5445
Additional Information:© 2002 Elsevier Science B.V. Received 17 April 2001, Accepted 19 November 2001, Available online 28 December 2001. We thank all the staff (technicians, researchers, engineers and students) of the Instituto Geofı́sico of the Escuela Politécnica Nacional of Quito (IG-EPN) for the monitoring and maintenance of the seismological stations in Ecuador and for the 24-h surveillance during the 2-year crisis of the Guagua Pichincha volcano. We thank the Institut Français d'Etudes Andines (IFEA), the Institut de Recherche pour le Développement (IRD) and the Ministère des Affaires Etrangères (MAE) for supporting portions of this study. We also thank Pr. Armando Cisternas for providing us with his code to calculate the stress tensor from focal mechanisms. Our thanks as well to Daniel Andrade, Nicole Béthoux, Erwan Bourdon, Jean-Philippe Eissen, Marc-André Gutscher, Jean-Luc Le Pennec, Michel Monzier and Daniel Rouland for the useful comments and discussions in the manuscript. We thank G. De Natale and C. Musumeci for reviewing this article with constructive and helpful remarks. Al amigo, Diego Viracucha, quien cayó el domingo 14 Enero del 2001 en el crater del Guagua Pichincha. Un recuerdo sincero para todos tus efuerzos y devoción a la volcanologı́a. Te dedicamos este pequeño trabajo.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Institut Français d'Etudes AndinesUNSPECIFIED
Institut de Recherche pour le Développement (IRD)UNSPECIFIED
Ministère des Affaires EtrangèresUNSPECIFIED
Subject Keywords:Stress tensor; Volcanic and tectonic swarm; Guagua Pichincha volcano; Ecuador
Issue or Number:1-2
Record Number:CaltechAUTHORS:20171128-132156892
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20171128-132156892
Official Citation:D Legrand, A Calahorrano, B Guillier, L Rivera, M Ruiz, D Villagómez, H Yepes, Stress tensor analysis of the 1998–1999 tectonic swarm of northern Quito related to the volcanic swarm of Guagua Pichincha volcano, Ecuador, In Tectonophysics, Volume 344, Issues 1–2, 2002, Pages 15-36, ISSN 0040-1951, https://doi.org/10.1016/S0040-1951(01)00273-6. (http://www.sciencedirect.com/science/article/pii/S0040195101002736)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83534
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:28 Nov 2017 21:31
Last Modified:09 Mar 2020 13:19

Repository Staff Only: item control page