Design of an optimal seismic network for monitoring geothermal fields

The reliable monitoring and location of the seismic activity at a local and regional scale is a key factor for hazard assessment. The exploitation of a geothermal field can be affected by natural and induced seismicity, hence optimal planning of a seismic network is of great interest for geothermal development.
Seismic monitoring depends on two main aspects: i) sensitivity of the seismic network and ii) the effectiveness of detection and location methods.
In this study, we focus on the first aspect proposing and improvement of an algorithm for the optimization of seismic networks designed for monitoring the seismic activity related to the injection test that will be performed in a geothermal well.
The algorithm is based on the method proposed by Tramelli et al. (2013) that tries to find the optimal station positions minimizing the volume of the error ellipsoid of the location for synthetic events using the D-criterion (Rabinowitz and Steinberg, 2000).
In this version of the program we improve the algorithm to find an optimal seismic network considering several prior information such as: 1) maps of seismic noise levels at different frequency bands, 2) three-dimensional seismic models and 3) topographic gradient of the study region. This information is usually produced during the exploration stage of a geothermal site and available prior an injection test.
We applied the methodology to the Acoculco geothermal field (Mexico) where an injection test is planned. In this work, we show a comparison between the standard approach that uses 1D seismic models, constant values of noise levels, and no topographic effects, with the new one showing how important is to consider these parameters for a more suitable optimization of the seismic network.
This work is performed in the framework of the Mexican European consortium GeMex (Cooperation in Geothermal energy research Europe-Mexico, PT5.2 N: 267084 funded by CONACyT-SENER : S0019, 2015-04, and of the joint agreement between UNAM and INGV on the development of seismological research of volcanic and geothermal field (N:44753-1023-22-IV-16/1).