Seismic networks layout optimization for a high-resolution monitoring of induced micro-seismicity

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ORIGINAL ARTICLE

Seismic networks layout optimization for a high-resolution monitoring of induced micro-seismicity Grazia De Landro & Matteo Picozzi & Guido Russo & Guido Maria Adinolfi & Aldo Zollo

Received: 15 May 2019 / Accepted: 24 September 2019 # Springer Nature B.V. 2019

Abstract The continuous monitoring of the spacetime-magnitude evolution of seismicity is a crucial task to assess the geo-mechanical conditions of hydrocarbon reservoirs. It is fundamental to design optimized highsensitivity and cost-effective seismic networks able to detect and locate low magnitude events with high accuracy. In Italy, after the concern for the 2012 Emilia earthquake, the government released the guidelines for monitoring the seismicity in areas surrounding subsurface industrial activities. In this work, we propose an optimization study for seismic monitoring networks based on the guideline requirements. We evaluated the performance, in terms of detection/location thresholds and events location errors, of different network layouts constructed by varying the station density and geometry and considering also the integration of seismic arrays. We simulated sets of seismic sources at different depths by varying magnitude and stress drop values. We considered two different values of noise level at the stations. The results show that the station density and the noise level represent the crucial parameters for the seismic network performances. The performances of a standard network comply the guidelines requirements in terms of detection/location thresholds. Only the integration of seismic networks with arrays allows to decrease the location errors of several hundreds of meters and to reach the location accuracy required by the Italian G. De Landro (*) : M. Picozzi : G. Russo : G. M. Adinolfi : A. Zollo Department of Physics “Ettore Pancini”, University of Naples “Federico II”, Napoli, Italy e-mail: [email protected]

guidelines. We foresee the integration of standard networks with seismic arrays to achieve high performance in terms of detection capability and location accuracy. Keywords Induced seismicity . Hydrocarbon reservoirs monitoring . Optimized seismic network . Seismic arrays . Minimum detectable/locatable magnitude . Ultramicro-seismicity detection . Monitoring guidelines

1 Introduction Monitoring earthquakes in areas interested by hydrocarbon exploitation or water fluid injection/extraction for energy development is a crucial task, due to the deep socio-economic implications related to the induced seismicity occurrence (Ellsworth 2013; Davies et al. 2013). Seismic monitoring, indeed, allows characterizing the seismicity in the subsurface volume where industrial exploitation activities take place. The main target of seismic monitoring is twofold: to allow the discrimination of natural from man-induced seismicity; to allow tracking the space-time-magnitude evolution of the seismicity and thus, if needed, to re-modulate, interrupt (in the foreseen cases), or restart industrial activities. Regarding the seismicity