News
Dr. David Eaton will give a webinar on October 17
Denver Geophysical Society
Microseismic Study Group
“What Controls the Magnitude of Injection-induced Earthquakes?”
Presented via webinar by
Dave Eaton, University of Calgary
October 17, 2017
TIME: 11:30 am – 12:30 pm Mountain Daylight Time
THIS IS A WEBINAR – WE ARE NOT MEETING AT PINNACLE/HALLIBURTON
Registration URL: https://attendee.gotowebinar.com/register/8193201495870546946
Webinar ID: 596-670-699
ATTENDANCE WILL BE LIMITED TO 100 PEOPLE
The October, 2017 Microseismic Study Group will be a webinar presented by Dave Eaton of the University of Calgary. The meeting is will be 11:30 a.m. Denver time – the normal time of Microseismic Study Group meetings. Attendance will be limited to 100 people, in the order of registration.
Abstract:
Three different approaches for estimation of maximum magnitude are considered here, along with their implications for managing risk. The first approach is based on a deterministic limit for seismic moment proposed by McGarr (1976), which was originally designed for application to mining-induced seismicity. This approach has since been reformulated for earthquakes induced by fluid injection (McGarr, 2014). In essence, this method assumes that the upper limit for seismic moment release is constrained by the pressure-induced stress change. A deterministic limit is given by the product of shear modulus and the net injected fluid volume. This method is based on the assumptions that the medium is fully saturated and in a state of incipient failure. An alternative geometrical approach was proposed by Shapiro et al. (2011), who postulated that the rupture area for an induced earthquake falls entirely within the stimulated volume. This assumption reduces the maximum-magnitude problem to one of estimating the largest potential slip surface area within a given stimulated volume. Finally, van der Elst et al. (2016) proposed that the maximum observed magnitude, statistically speaking, is the expected maximum value for a finite sample drawn from an unbounded Gutenberg-Richter distribution. These three models imply different approaches for risk management. The deterministic method proposed by McGarr (2014) implies that a ceiling on the maximum magnitude can be imposed by limiting the net injected volume, whereas the approach developed by Shapiro et al. (2011) implies that the time-dependent maximum magnitude is governed by the spatial size of the microseismic event cloud. Finally, the sample-size hypothesis of van der Elst et al. (2016) implies that the best available estimate of the maximum magnitude is based upon observed seismicity rate. The latter two approaches suggest that real-time monitoring is essential for effective management of risk. A reliable estimate of maximum plausible magnitude would clearly be beneficial for quantitative risk assessment of injection-induced seismicity.
References
McGarr, A. 1976. Seismic moments and volume changes. Journal of Geophysical Research, 81(8), 1487–1494.
McGarr, A. 2014. Maximum magnitude earthquakes induced by fluid injection. Journal of Geophysical Research: Solid Earth, 119(2), 1008–1019.
Shapiro, S.A., Kruger, O.S., Dinske, C., and Langenbruch, C. 2011. Magnitudes of induced earthquakes and geometric scales of fluid-stimulated rock volumes. Geophysics, 76(6), WC55–WC63.
van der Elst, N.J., Page, M.T., Weiser, D.A., Goebel, T.H.W., and Hosseini, S.M. 2016. Induced earthquake magnitudes are as large as (statistically) expected. Journal of Geophysical Research: Solid Earth, 121(6), 4575–4590.