Abstract
AbstractThe Reykjanes Geothermal System (RGS) is a high‐temperature geothermal system located on the Reykjanes peninsula, a transtensional plate‐boundary zone located on the southwestern tip of Iceland. The area is characterized by high seismicity, recent volcanism, and high‐temperature geothermal fields. We use seismic noise records from April 2014 to August 2015 to study stress changes and potential deformation of the subsurface caused by injection and production operations at RGS through seismic interferometry. We retrieve continuous time series of waveform similarity values and seismic velocity changes during this period. The S‐transform of the similarity values allows us to clearly identify three variations in the mechanical properties of the Reykjanes peninsula related to rapid changes of RGS production. In addition, we observe a slow seismic velocity decrease of 0.36%/year in the reservoir due to the water deficit and seasonal variations associated with the energy production demand.
Highlights
Despite the fact that early foundations have been laid in the 50s and 60s by seismologists such as Aki (1957) and Claerbout (1968), seismic interferometry (SI) gained most of its popularity over the last decade
The Reykjanes Geothermal System (RGS) is a high‐temperature geothermal system located on the Reykjanes peninsula, a transtensional plate‐boundary zone located on the southwestern tip of Iceland
We identify and locate three short‐term variations associated with abrupt injection and production rate changes in Reykjanes Geothermal System
Summary
Despite the fact that early foundations have been laid in the 50s and 60s by seismologists such as Aki (1957) and Claerbout (1968), seismic interferometry (SI) gained most of its popularity over the last decade. The main condition required for monitoring is that the ambient vibrations are statistically robust over certain time windows This permits repeatable virtual source responses, which allow for structural changes to be studied. Due to this characteristic, the condition that the medium is illuminated uniformly from all angles, which is a requirement for accurate Green's function retrieval (Tsai, 2009; Weaver et al, 2009), can be relaxed for monitoring purposes (Hadziioannou et al, 2009). We assess the capability of SI to detect tiny mechanical and structural changes in RGS using ambient‐seismic noise recorded by thirteen stations from April 2014 till August 2015 (Figure 1) During this period, the geothermal activity of the power plant was uninterrupted in different points of the peninsula. We propose a new procedure to discriminate potential changes in time and frequency of such evolution curves through the computation of the S transform (Stockwell et al, 1996)
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