Detecting Elevated Pore Pressure due to Wastewater Injection Using Ambient Noise Monitoring

Zhuo Yang,Congcong Yuan,Marine A Denolle

doi:10.1785/0320210036

Abstract

Abstract The injection of large volumes of wastewater has induced earthquakes from June 2010 to July 2011 along the Guy–Greenbrier fault in Arkansas. We measure time-dependent changes in seismic velocities underneath three temporary seismic stations, using the daily autocorrelations of ambient seismic noise. We do not find any effect of the pumping rate or volume injected in the changes in velocity. However, the induced earthquakes’ ground motions are associated with an extreme reduction in seismic velocities. The magnitude of the changes surpasses ten times the values typically found in other earthquake settings. Our full-waveform investigation suggests that the changes mainly occurred around the top of the Ozark aquifer. We interpret these extreme changes as a result of dynamic shaking in the elevated pore pressure system of the Ozark aquifer.

Highlights

Induced seismicity has shaken the communities of central United States with the surge of events in an otherwise seismically quiet region
A well-studied case of seismicity induced by wastewater injection is the reinitiation of the Guy–Greenbrier fault (GGF), which has hosted several earthquakes of magnitudes greater than 4 in the years 2009–2011 (Horton, 2012; Mousavi et al, 2017)
Most of the seismicity occurs on the GGF, in the Precambrian basement, well below the Ozark aquifer and the depth of the wastewater injection wells

Summary

Introduction

Induced seismicity has shaken the communities of central United States with the surge of events in an otherwise seismically quiet region. Recent studies of fluid injection near the GGF have modeled elevated pore pressure as high as 0.1 MPa at a depth of the seismicity, at the tip of the injected well SRE (1.9 km depth), and have modeled the flow of fluid within the Ozark aquifer and Precambrian basement (Ogwari and Horton, 2016; Yehya et al, 2018) Based on both numerical simulations and laboratory studies, the large stresses generated by coseismic ruptures can dilate existing and form new cracks, thereby increasing the porosity in the fault zone and decreasing the seismic velocity of both P and S waves (Kaproth and Marone, 2014).

Findings

Discussion

Conclusions