Location and Felt Reports for the 25 April 2010 mbLg 3.9 Earthquake near Alice, Texas: Was it Induced by Petroleum Production?

Abstract

This study examines seismograms and felt reports for the 25 April 2010Alice, Texas, earthquake and explores its possible relationship with gas and oil production in the Stratton field. We identified P arrivals at seven broadband stations situated within ∼100 km of the epicentral region and determined a location of 27.72°N, 97.95°W, about 11 km east of the location reported by the National Earthquake Information Center but coincident with the region of highest intensity (modified Mercalli intensity V-VI) felt reports. We compare arrivals for observed secondary P and S arrivals with predictions from a published Gulf Coast velocity model. At nearby stations, the secondary arrivals are much stronger than primary arrivals; the arrival times and the presence of high-amplitude phases traveling at the Love-wave velocity of the uppermost model layer suggest the focal depth was shallow, 3 km or less. This places the 2010 hypocenter approximately along the mapped trace of the Vicksburg fault zone and at the depth of the Frio formation, the principal productive member in the Stratton field, which has produced at least 2.7 trillion cubic feet of gas and about 100 million barrels of oil since production commenced in 1938. We conclude it is plausible, although not proven definitively, that production in the Stratton field contributed to the occurrence of the 2010 Alice earthquake and an earlier similar earthquake that occurred on 24 March 1997.

A Historical Review of Induced Earthquakes in Texas

“…6 and 12); on 17 May 2012, there was a larger M w 4.8 event that produced intensities up to MMI VII. Waveform modeling for the 17 May mainshock was consistent with a focal depth of 4.5 km (Frohlich et al, 2014). Focal mechanisms reported for this event indicated strike-slip faulting (Fig.…”

“…This is particularly true for three recent sequences of earthquakes associated with wastewater disposal in deep wells. These are the DFW International Airport sequence of 2008-2013 , the Timpson sequence surrounding the M w 4.8 earthquake of 17 May 2012 (Frohlich et al, 2014), and the Azle sequence beginning in 2013 (Hornbach et al, 2015). All three sequences occurred in regions where prior seismic activity was unknown; all three had accurately determined epicenters situated within about 2 km of active injection wells with maximum monthly injection rates of 24; 000 m 3 or greater; all three sequences had accurately determined hypocenters with focal depths at approximately the depth of injection and at greater depths; and epicenters for all three sequences occurred within a few kilometers of known mapped subsurface faults.…”

“…The location labeled crack indicates the reported location of a 1.6-km-long northeast-southwest crack following the 1997 earthquake. Symbols +, ×, and *, respectively, indicate the NEIC epicenters for the 1997 and 2010 earthquakes and the location for both events as determined by Frohlich et al (2012). Dark and light gray areas are oil and gas fields, respectively; mapped faults are from Ewing (1990).…”

“…By February 2013, eight temporary seismograph stations had been installed (Frohlich et al, 2014). These stations recorded numerous aftershocks with epicenters situated along a northwest-southeast-trending, southwest-dipping mapped fault that had been reported by Jackson (1982).…”

“…The aftershock sequence was situated about 2-3 km from two wastewater injection wells that had been injecting 16; 000 m 3 =mo or more since 2006-2007 at depths of about 1.9 km. A search of records at station NATX in Nacogdoches (about 35 km distant) revealed that several small earthquakes, apparently from the same focus, had occurred in 2008, 2010, and 2011 (Frohlich et al, 2014), and subsequent reanalysis of Transportable Array data revealed additional earthquakes that occurred between 2010 and 2012 (Walter et al, 2016). Fan et al (2016) simulated the spatial and temporal evolution of the pore pressure and stress fields in this region using a coupled finite-element geomechan-▴ Figure 11.…”