eprintid: 1841
rev_number: 17
eprint_status: archive
userid: 6
dir: disk0/00/00/18/41
datestamp: 2017-03-02 10:59:38
lastmod: 2017-05-16 12:39:47
status_changed: 2017-03-02 10:59:38
type: article
metadata_visibility: show
creators_name: Viegas, Gisela
creators_name: Hutchings, Lawrence
corp_creators: Lawrence Berkeley National Lab
corp_creators: Lawrence Berkeley National Lab
title: Source Characteristics of Micro-Earthquakes at the Northwest Geysers Geothermal Field, California
subjects: MP2
subjects: RU1_1
subjects: SG
divisions: SHEER-5
full_text_status: none
keywords: Geysers, micro-earthquakes, induced seismicity, earthquake source, stress drop, radiated energy, Empirical Green’s function
abstract: We investigate the source parameters of micro-earthquakes (<M3) at the Northwest Geysers, near an injection well, before and during water injection, looking for temporal and spatial variations. Our objective is to understand the relation among injection, production and source mechanisms of micro-earthquakes. To determine the source parameters of the micro-earthquakes, such as fault radius, stress drop, seismic moment and radiated energy, we use two techniques: the Empirical Green’s Function (EGF) method; and the NetMoment method, and compare the source parameters results of micro-earthquakes used in both studies. Our results indicate that micro-earthquakes at the Northwest Geysers have on average small radius and large stress drops (median of 27.7 MPa). The stress drops of these induced micro-earthquakes are comparable to the ones of deeper, large (>M5.5), natural occurring tectonic earthquakes. Possible explanations for the high stress drop are, for example, fault re-strengthening by geochemical alteration or the fracturing of intact rock induced by the injection of cold water. This source information has implications for understanding the physics of faulting and for seismic potential assessment in areas of ongoing geothermal exploration.
date: 2010-12
date_type: published
publication: Geothermal Resources Council Transactions
volume: 34
publisher: Geothermal Resources Council
pagerange: 1265-1272
issn: 0193-5933
official_url: https://www.geothermal-library.org/index.php?mode=pubs&action=view&record=1028823
access_IS-EPOS: limited
owner: Publisher
citation:   Viegas, Gisela and Hutchings, Lawrence  (2010) Source Characteristics of Micro-Earthquakes at the Northwest Geysers Geothermal Field, California.  Geothermal Resources Council Transactions, 34.  pp. 1265-1272.