Development of seismicity and probabilistic hazard assessment for the Groningen gas field

Abstract

The increase in number and strength of shallow induced seismicity connected to the Groningen gas field since 2003 and the occurrence of a M L 3.6 event in 2012 started the development of a full probabilistic seismic hazard assessment (PSHA) for Groningen, required by the regulator. Densification of the monitoring network resulted in a decrease of the location threshold and magnitude of completeness down to ∼ M L = 0.5. Combined with a detailed local velocity model, epicentre accuracy could be reduced from 0.5-1 km to 0.1-0.3 km and a vertical resolution ∼0.3 km. Time-dependent seismic activity is observed and taken into account into PSHA calculations. Development of the Ground Motion Model for Groningen resulted in a significant reduction of the hazard. Comparison of different implementations of the PSHA, using different source models, based on either a compaction model and production scenarios or on extrapolation of past seismicity, and methods of calculation, shows similar results.

The effect of imposed production measures on gas extraction induced seismic risk

“…Detailed information on the Groningen network and dataset can be found in Dost et al (2017). The network of seismometers in the Groningen region was designed to be complete for earthquakes above magnitudes of 1.5.…”

“…Although Dost et al (2017) derived a time dependence in M c due to the extension of the network, for consistency and ease of comparison we used M c = 1.2 for the full catalogue between 1995 and 2017. The total number of events N (M ≥ M c ) in each bin has been constrained to the total number of 56 (M ≥ M c )-events that occurred in the years 2015 and 2016 combined.…”

From checking deterministic predictions to probabilities, scenarios and control loops for regulatory supervision

“…The NAM-predicted maximum subsidence at the end of field life went to 77 cm in 1973 and then to 30 cm in 1977. In 1984 the prediction went up again to 65 cm, down to 36 cm in 1990 and then via 38 cm (1995) and 42 cm (2005) For induced seismicity also, what happened was very different from the original expectations (Dost et al, 2017). It took many years before the causal relationship between seismicity and the gas production was widely accepted, illustrating the strength of paradigms.…”

“…1). The figure suggests that smaller events probably started earlier without being detected, given the limitations of the seismic network (Dost et al, 2017) at the time.…”

Ground-motion networks in the Groningen field: usability and consistency of surface recordings

“…An overview of the historical development of the permanent Groningen recording networks is provided by Dost et al (2017). The purpose of this paper is to present some more details about the characteristics of the networks and the instruments with a view to providing insight into the usability of the growing number of recordings, which form an exceptional database of ground motions from induced earthquakes.…”