eprintid: 1286 rev_number: 15 eprint_status: archive userid: 2 dir: disk0/00/00/12/86 datestamp: 2015-02-25 09:25:04 lastmod: 2017-09-20 12:36:12 status_changed: 2015-04-27 12:10:37 type: article metadata_visibility: show creators_name: Frohlich, Cliff creators_name: Hayward, C. creators_name: Stump, B. creators_name: Potter, E. creators_id: cliff@ig.utexas.edu creators_id: creators_id: creators_id: corp_creators: Institute for Geophysics Jackson School of Geosciences University of Texas at Austin 10100 Burnet Rd. (R2200) Austin, Texas 78758-4445 corp_creators: Huffington Department of Earth Sciences Southern Methodist University Dallas, Texas 75275 corp_creators: Bureau of Economic Geology Jackson School of Geosciences University of Texas at Austin Austin, Texas 78758 title: The Dallas-Fort Worth Earthquake Sequence: October 2008 through May 2009 ispublished: pub subjects: RU2 subjects: SHU subjects: SS divisions: EPOS-P full_text_status: none abstract: This paper describes a sequence of small earthquakes (mb≤3.3) that occurred at the Dallas–Fort Worth Airport, Texas, between 30 October 2008 and 31 May 2009. Analysis of records at regional station WMOK identified more than 180 earthquakes in the sequence; about 90 percent occurred in four clusters on 30 October–1 November, 20 November, 26 December and 15–17 May. After the sequence began, a six-station temporary local network obtained high-quality three-component records for 11 earthquakes occurring between 20 November and 1 December. Analysis of these data demonstrated that all 11 earthquakes originated from a focus near 32.855° N, 97.051° W, with an estimated depth ∼4.4 km. This location is less than 0.5 km from a well completed in August 2008 that extends to a depth of 4.2 km, drilled to dispose of brines collected during flowback of hydraulic fracturing fluids associated with the production of natural gas. Brine disposal commenced at the well on 12 September 2008. Seismograms and (S-P) intervals for the earthquakes are similar though not identical, and relative locations indicate they occurred along a north-northeast–south-southwest trend with horizontal and vertical dimensions of ∼1.1 km and 0.2 km, respectively. This trend is approximately coincident with that of a mapped normal fault in the subsurface, and consistent with the maximum horizontal in situ stress direction. Because of the absence of previous historical earthquakes, the proximity of the brine disposal well, and the similarity with other documented cases of induced seismicity, it seems likely that fluid injection induced the 2008–2009 sequence. date: 2011-02 date_type: published publication: Bulletin of the Seismological Society of America volume: 101 number: 1 publisher: Seismological Society of America pagerange: 327-340 id_number: doi:10.1785/0120100131 refereed: TRUE issn: 0037-1106 official_url: http://dx.doi.org/10.1785/0120100131 access_IS-EPOS: limited owner: Publisher citation: Frohlich, Cliff and Hayward, C. and Stump, B. and Potter, E. (2011) The Dallas-Fort Worth Earthquake Sequence: October 2008 through May 2009. Bulletin of the Seismological Society of America, 101 (1). pp. 327-340. DOI: https://doi.org/10.1785/0120100131