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Modelling Induced Seismicity in the Hengill Geothermal Field

Description: 

The Hengill Geothermal Field is located in Southwest Iceland and hosts the Hellisheiði and Nesjavellir power plants. The area is characterized by a complex triple junction between three tectonic features: the Reykanes Peninsula rifting, South Iceland Volcanic Zone and West Volcanic Zone. The geothermal field comprises 60+ production wells and 17 injection wells. Significant seismicity, both natural (volcanic uplift event in the 1990s) and production/injection induced is recorded.
The beginning of the reinjection in the Húsmúli area in 2011 was associated to a seismic crisis. A high resolution catalogue covering the first nine months of injection allows us to have a look at the dynamics of the seismicity and to characterise the fractures and state of stress of the area. We attempt to model this onset of induced seismicity using a hybrid coupled hydro-geomechanical model (TOUGH2-Seed).
In the framework of the Geothermica project COSEISMIQ (http://www.coseismiq.ethz.ch/en/home/), a dense temporary network was installed to monitor the seismicity in the Hengill region between December 2018 and August 2021. With this enhanced network, novel analysis and relocation techniques, a high resolution relocated catalogue was curated and comprises around 8500 events in the Hengill area.
We use a Seismogenic index type model and different flavours of Epidemic Type Aftershock Sequence (ETAS) to model the natural and induced seismicity during the two and a half year period. We employ a pseudo-forecasting approach and compare models performances and fit to the recorded seismic data to assess the strengths and weaknesses of the different models.

Session: Understanding and Managing Induced Seismicity

Type: Oral

Date: 4/19/2023

Presentation Time: 02:30 PM (local time)

Presenting Author: Vanille A. Ritz

Student Presenter: Yes

Invited Presentation: 

Authors