Induced Seismicity Completeness Analysis for Improved Data Mining

Abstract

The study of induced seismicity at sites of fluid injection is paramount to assess the seismic response of the earth’s crust and to mitigate the potential seismic risk. However statistical analysis is limited to events above the completeness magnitude mc, which estimation may significantly vary depending on the employed method. To avoid potential biases and optimize the data exploitable for analysis, a better understanding of completeness, detection capacity and censored data characteristics is needed. We apply various methods previously developed for natural seismicity on 16 underground stimulation experiments. We verify that different techniques yield different mc values and we suggest using the 90% quantile of the mc distribution obtained from high-resolution mapping, with mc defined from the mode of local magnitude frequency distributions (MFD). We show that this distribution can be described by an asymmetrical Laplace distribution and the bulk MFD by an asymmetric Laplace mixture model. We obtain an averaged Gutenberg-Richter parameter b=1.03±0.48 and a detection parameter k=3.18±1.97 from mapping, with values subject to high uncertainties across stimulations. We transfer Bayesian mc mapping developed for natural seismicity to the context of induced seismicity, here adapted to local three-dimensional seismicity clouds. We obtain the new prior parameterization mc,pred=1.64log10(d3)−1.83, with d3 the distance to the 3rd nearest seismic station. The potential use of censored data and of mc prediction is finally discussed in terms of data mining to improve the monitoring, modeling and managing of induced seismicity.

Comprehensive Survey of Seismic Hazard at Geothermal Sites by a Meta-Analysis of the Underground Feedback Activation Parameter afb

“…Our survey consisted in finding all underground stimulation experiments related to geothermal energy harnessing. We first used the lists of projects provided in existing reviews [22][23][24][25][26] and then complemented our research with an additional Google Scholar search for "injection induced seismicity geothermal". We obtained a comprehensive list of 53 fluid injections worldwide, which are described in Table A1, including matching references and relevant quotes from a total of 44 articles and reports.…”

“…To investigate the m 0 ambiguity, we consider the magnitude-frequency distribution defined by Mignan [29], shown to also be valid for induced seismicity [26]:…”

“…with n i and n c non-cumulative counts of earthquakes for the incomplete and complete magnitude ranges, respectively, and k a detection parameter, found to be ≈ 3 for both natural [29] and induced seismicity [26]. We obtain from Equation ( 2)…”

“…. A total amount of 13,000 m 3 of water was injected" [45] (p. 1000); b = 4.14 [26] (Table 2) not included, as estimated from less than 30 events. 09hn Hannover HYDRAULIC STIMULATION, "Microseismic (1.8 M)" [24] (Table 1).…”

“…Of these events 349 were strong enough to be located" [63] (p. 1025); −1.1 ≤ ML(corr) ≤ 3.5 [63] (Figure 6). NB: Important role of gas kick overpressure; b = 0.83 [26] (Table 2).…”