Pseudo-prospective forecasting of induced and natural seismicity in the
Hengill geothermal field
Abstract
The Hengill geothermal field, located in southwest Iceland, is host to
the Hellisheiði power plant, with its 40+ production wells and 17
reinjection wells. Located on a tectonically active area, the field
experiences both natural and induced seismicity linked to the power
plant operations. To better manage the risk posed by this seismicity,
the development of robust and informative forecasting models is
paramount.
In this study, we compare the forecasting performance of a model
developed for fluid-induced seismicity (the Seismogenic Index model) and
a class of well-established statistical models (Epidemic-Type Aftershock
Sequence). The pseudo-prospective experiment is set up with 14 months of
initial calibration and daily forecasts for a year.
In the timeframe of this experiment, a dense broadband network was in
place in Hengill, allowing us to rely on a high quality relocated
seismic catalogue. The seismicity in the area is characterised by four
main clusters, associated with the two reinjection areas, one production
area an area with surface geothermal manifestations but where no
operations are taking place.
We show that the models are generally well suited to forecast induced
seismicity, despite some limitations, and that a hybrid ETAS accounting
for fluid forcing has some potential in complex regions with natural and
fluid-induced seismicity.