Application of the EtAs seismostatistical Model to Microseismicity From Geothermal Fields
Application of the EtAs seismostatistical Model to Microseismicity From Geothermal Fields
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发表时间：
2013
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通讯作者：
T. Eto;H. Asanuma;M. Adachi;K. Saeki;Kengo Aoyama;Hitoshi Ozeki;Y. Mukuhira;M. Häring
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作者：
T. Eto;H. Asanuma;M. Adachi;K. Saeki;Kengo Aoyama;Hitoshi Ozeki;Y. Mukuhira;M. Häring
以感觉地震的形式诱发地震活动的发生已被认为是与最近地热开发相关的关键环境负担之一。由于这个原因，研究能够对较大震级诱发的事件进行风险评估的技术已越来越受到重视。在本研究中，我们将地震统计建模方法应用于两个地热田的微地震数据，并探讨了其风险评估的可行性。本文采用在自然地震学领域广泛应用的流行型余震序列（ETAS）模型（Ogata, 1988）作为地热地震风险评估研究的第一步。利用ETAS成功地模拟了日本最大的热液地热田之一柳井unishiyama的微震活动。瑞士巴塞尔EGS站点的诱发地震活动也用ETAS进行了模拟，在这种情况下使用了短的移动时间窗口，因为整个地震活跃期的建模是不成功的。我们的研究表明，ETAS模型中的一个参数，以前被解释为代表由外部强迫触发的事件的发生率（Hainzl和Ogata， 2005），在我们的两个案例中都可以与每个油藏的处理/增产注入速率相关。我们的初步结果表明，地震统计建模在评估与地热储层中各种人为操作相关的感觉地震风险方面是可行的，尽管还需要进一步调查和模拟诱发地震活动的行为。
The occurrence of induced seismicity in the form of felt earthquakes has been recognized as one of the critical environmental burdens associated with recent geothermal development. For this reason, research into enabling technologies for risk assessment of larger magnitude induced events has taken on an increased priority. In this study, we have applied a seismostatistical modeling method to microseismic data collected at two geothermal fields and have investigated its feasibility for risk assessment. Here we have applied the Epidemic Type Aftershock Sequence (ETAS) model (Ogata, 1988), which has been widely used in the area of natural seismology, as a first step in this geothermal earthquake risk assessment study. The microseismicity observed at YanaizuNishiyama, one of the largest hydrothermal geothermal fields in Japan, has been successfully modeled with ETAS. Induced seismicity at the Basel EGS site in Switzerland was also modeled with ETAS, in this case using short moving time windows since modeling for the whole seismically active period was unsuccessful. Our study suggests that one of the parameters in the ETAS model, which has previously been interpreted to represent the occurrence rate of events triggered by external forcing (Hainzl and Ogata, 2005), can in both our cases be correlated with the treatment/stimulation injection rate into each reservoir. Our preliminary results demonstrate the feasibility of seismostatistical modeling in assessing the risks of felt earthquakes associated with various human operations in geothermal reservoirs, although further investigation and modeling of behavior of induced seismicity is required.