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Hindcasting the 1993 - 2023 Wirdum Induced Earthquake Sequence

Description: 

On October 8th 2022, a ML 3.1 earthquake struck the village of Wirdum, 20 km from the city of Groningen in the Netherlands. The earthquake could be linked to a 4.3 km fault cross-cutting a gas reservoir, the Wirdum fault. The Wirdum fault segment experienced over 30 prior earthquakes since its reactivation due to gas production, including a ML 2.5 (2019) and a ML 2.7 (2015). Current hazard models lack the capability of both hindcasting a sequence of induced earthquakes over decades and studying the source and surface processes. For this a physics-based prediction framework is needed. Using high-quality data of the Groningen gas field, we re-interpreted the fault geometry. Constrained by well-log data we load the realistic fault geometry with heterogeneous pre- and post-production stresses using a semi-analytical 2.5D poroelastic stress solution (PANTHER; Buijze, 2024). Based on extensive laboratory experiments we use heterogeneous friction and elastic parameters to account for variable along-strike on-fault reservoir offset and bi-material regions, embedded in a detailed geological model. We derive the critical stress levels at which we simulate the three ML 2.5+ earthquakes of the Wirdum sequence through data-driven 3D dynamic rupture modelling (SeisSol). Results show predicted critical levels of on-fault stresses similar to observed reservoir pressure at times of each earthquake. Each earthquake nucleates spontaneously through stress loading. Simulated hypocentres are controlled most by variations in fault dip (its first M1’s), although other fault geometry aspects are important as well. Rupture arrest is dominantly controlled by on-fault stress heterogeneity resulting from along-strike kilometre-scale undulations of the fault geometry. Calculated first arrivals for each earthquake largely agree with observed seismograms. This physics-based hindcasting framework for induced seismicity will be used to forecast future earthquakes on the Wirdum fault. We will build forth on this for seismic hazard assessment and Mmax estimates in Groningen and towards a successful contribution of sustainable subsurface solutions.

Session: Induced Earthquakes: Source Characteristics, Mechanisms, Stress Field Modeling and Hazards [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Vincent

Student Presenter: Yes

Invited Presentation: 

Authors