Anthropogenic seismicity as aftershocks for geo-resource production? Implications for Mmax estimates (reservoir impoundment cases)

Abstract

SUMMARY Developing a model for anthropogenic seismic hazard remains an open challenge whatever the geo-resource production. We analyse the (Mmax) largest reported magnitude on each site where (RTS) Reservoir Triggered Seismicity in documented (37 events, 1933–2008), for aftershocks of reservoir impoundment loading. We relate each reservoir impoundment to its magnitude-equivalent M*reservoir = M*(Lr). We use (Lr) the reservoir length as a proxy for a rupture length of the reservoir main shock-equivallent. This latter is derived from the empirical relationship that exists for tectonic earthquake among magnitude and rupture length. We resolve (i) Mmax for RTS are bounded by M*reservoir at a 95 per cent confidence level; (ii) in average Mmax are smaller than M*reservoir by 2.2 units (iii) 50 per cent of the Mmax occurrence is within 2 ± 1 yr from the reservoir impoundment. These triggering patterns support the signature of fluid driven seismicity during the slow reservoir impoundment emerges as a weaker efficiency (larger ΔM = M*reservoir – Mmax) to trigger Mmax events than from earthquake interactions.