From Induced Seismicity to Direct Time-Dependent Seismic Hazard

Abstract

The growing installation of industrial facilities for subsurface exploration worldwide requires continuous refinements in understanding both the mechanisms by which seismicity is induced by field operations and the related seismic hazard. Particularly in proximity of densely populated areas, induced low-to-moderate magnitude seismicity characterized by high-frequency content can be clearly felt by the surrounding inhabitants and, in some cases, may produce damage. In this respect we propose a technique for time-dependent probabilistic seismic-hazard analysis to be used in geothermal fields as a monitoring tool for the effects of on-going field operations. The technique integrates the observed features of the seismicity induced by fluid injection and extraction with a local ground-motion prediction equation. The result of the analysis is the time-evolving probability of exceedance of peak ground acceleration (PGA), which can be compared with selected critical values to manage field operations. To evaluate the reliability of the proposed technique, we applied it to data collected in The Geysers geothermal field in northern California between 1 September 2007 and 15 November 2010. We show that the period considered the seismic hazard at The Geysers was variable in time and space, which is a consequence of the field operations and the variation of both seismicity rate and b-value. We conclude that, for the exposure period taken into account (i.e., two months), as a conservative limit, PGA values corresponding to the lowest probability of exceedance (e.g., 30%) must not be exceeded to ensure safe field operations. We suggest testing the proposed technique at other geothermal areas or in regions where seismicity is induced, for example, by hydrocarbon exploitation or carbon dioxide storage

Developing an Application‐Specific Ground‐Motion Model for Induced Seismicity

“…This fact gives further weight to our argument that application-specific GMPEs must be developed for induced seismicity. Sharma et al (2013), following earlier work by Convertito et al (2012) for PGA, recognized the need for application-specific GMPEs and derived predictive equations for PGA, PGV, and SA for induced earthquakes in The Geysers geothermal field in California. The equation is a function of magnitude and hypocentral distance (R hyp ), with a stationspecific correction for site response.…”

“…The stochastic simulation-based models cover many combinations of values of the Brune (1970Brune ( , 1971) stress parameter, Q, and kappa (Anderson and Hough, 1984), in order to provide a framework for capturing epistemic uncertainty. However, in common with the Convertito et al (2012) model, they obtain rather large standard deviations (σlnPGA 1:30), possibly as a result of limited site classification information. As explained later, the approach we adopted for the Groningen field has many similarities with that used by Douglas et al (2013) but uses only application-specific data.…”

Violations of Gutenberg–Richter Relation in Anthropogenic Seismicity

“…[e.g. Lasocki, 1989;1993a,b;Kijko et al, 1993;Stewart and Spottiswoode, 1993;Trifu, et al, 1997;Convertito et al, 2012].…”

Time-dependent seismic hazard in Bobrek coal mine, Poland, assuming different magnitude distribution estimations

“…Spatial and temporal seismicity rate anomalies are essentially reported as the most frequent intermediate-term precursory phenomenon in timescales varying from a few days to several years. The use of the well-established Gutenberg-Richter (G-R) law has been routinely incorporated into many seismic hazard assessment studies (e.g., Cornell 1968;Convertito et al 2012). Alternatively, nonparametric approaches can be performed for hazard assessment evaluation under certain conditions (e.g., Kijko et al 2001;Lasocki and Orlecka-Sikora 2008).…”