Jan van Elk

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

Abstract A key element of quantifying both the hazard and risk due to induced earthquakes is a suite of appropriate ground‐motion prediction equations (GMPEs) that encompass the possible shaking levels due to such events. Induced earthquakes are likely to be of smaller magnitude and shallower focal depth than the tectonic earthquakes for which most GMPEs are derived. Furthermore, whereas GMPEs for moderate‐to‐large magnitude earthquakes are usually derived to be transportable to different locations and applications, taking advantage of the limited regional dependence observed for such events, the characteristics of induced earthquakes warrant the development of application‐specific models. A preliminary ground‐motion model for induced seismicity in the Groningen gas field in The Netherlands is presented as an illustration of a possible approach to the development of these equations. The GMPE is calibrated to local recordings of small‐magnitude events and captures the epistemic uncertainty in the extrapolation to larger magnitude considered in the assessment of the resulting hazard and risk.

Framework for a Ground-Motion Model for Induced Seismic Hazard and Risk Analysis in the Groningen Gas Field, The Netherlands

The potential for building damage and personal injury due to induced earthquakes in the Groningen gas field is being modeled in order to inform risk management decisions. To facilitate the quantitative estimation of the induced seismic hazard and risk, a ground motion prediction model has been developed for response spectral accelerations and duration due to these earthquakes that originate within the reservoir at 3 km depth. The model is consistent with the motions recorded from small-magnitude events and captures the epistemic uncertainty associated with extrapolation to larger magnitudes. In order to reflect the conditions in the field, the model first predicts accelerations at a rock horizon some 800 m below the surface and then convolves these motions with frequency-dependent nonlinear amplification factors assigned to zones across the study area. The variability of the ground motions is modeled in all of its constituent parts at the rock and surface levels.

Probabilistic damage assessment of buildings due to induced seismicity

Natural gas production in the Groningen field in the Netherlands is causing induced earthquakes that have raised concerns regarding the safety of the local population given that the exposed building stock (which is predominantly unreinforced masonry residential housing) has not been designed and constructed considering seismic loading. Significant effort has been invested to date in assessing the safety risk of these buildings within a probabilistic framework. This paper describes the efforts that have since been made to extend this framework for probabilistic damage assessment of the buildings, for slight non-structural, slight structural and moderate structural damage. Fragility functions for non-structural damage have been developed considering the observed damage from damage reports, rather than from damage claims due to a number of issues with the latter, as described herein. Structural damage has been estimated using analytical models that have been calibrated through extensive in situ data collection and experimental testing. The probabilistic damage assessment is presented in terms of F-N curves, which plot the annual frequency of exceedance against number of buildings reaching each damage state.