Long-term induced seismicity on the Mosha fault by Damavand Volcano, N-Iran, Implications on the seismic hazard of Tehran metropolis

A common challenge faced in underground hardrock mines worldwide is post mining-induced seismicity, as the events have been quite disastrous, causing risk to the structures and lives. In the recent years, many of the worked out mining areas are slowly getting populated and in due course of time shall be posing environmental threat to the people residing above and to the surface structures like sudden void formations or sudden ground collapse becoming visible on the surface. Worked out or closed mines have most of the time shown existence of post mining-induced seismicity signatures. Some of the closed mines showing post mining induced seismicity in Korea, South Africa, Sweden and India are being discussed. Post mining induced seismicity observed in Kolar Gold Fields worked out mine still being felt since closure of deeper levels is discussed. As mining depth increases especially in hard rock mines, magnitude of stress increases, hence, the occurrence and severity of postmining induced seismicity also increases. The problem becomes more serious if proper fund allocation is not done to investigate these areas, may be due to the absence of economic interest once the mine site has been abandoned and in many cases, direct investigations inside the mines may not be possible due to stability problems or due to the ingress of water into the void spaces of the mining area. Several approaches and techniques adopted by researcher’s world over are being discussed in this paper, with a view to gaining insight into the techniques of evaluation of seismic hazard. Seismic vulnerability assessment should integrate the effects of all the seismic events occurring at different locations of mining area during mining and post mining, along with their uncertainties also being considered. Based on the recorded data and some of the derived parameters from previous years, an attempt should be made to evaluate the existing risk prone areas. The past records of induced seismicity due to mining should be used as a precursor for identification of impending future events and their expected probable locations of occurrence. The methods discussed here for assessment of seismic hazard are based on direct waveform and seismic source parameters, parameters from indirect waveform methods, frequency-magnitude relationship based, and frequency content analysis based. From the assessment it is found that the choice of method that can be used depends on the period of monitoring (short-term monitoring, intermediate-term or long-term monitoring) and the objective of the study required to be achieved, this varies on site-to-site basis. The main focus is to show the importance and need to install a micro seismic monitoring system for long term assessment of seismic risk especially in abandoned/worked out mines showing post mining-induced seismicity.

AbstractSometimes, a rather high stress drop characterizes earthquakes induced by underground fluid injections or productions. In addition, long-term fluid operations in the underground can influence a seismogenic reaction of the rock per unit volume of the fluid involved. The seismogenic index is a quantitative characteristic of such a reaction. We derive a relationship between the seismogenic index and stress drop. This relationship shows that the seismogenic index increases with the average stress drop of induced seismicity. Further, we formulate a simple and rather general phenomenological model of stress drop of induced earthquakes. This model shows that both a decrease of fault cohesion during the earthquake rupture process and an enhanced level of effective stresses could lead to high stress drop. Using these two formulations, we propose the following mechanism of increasing induced seismicity rates observed, e.g., by long-term gas production at Groningen. Pore pressure depletion can lead to a systematic increase of the average stress drop (and thus, of magnitudes) due to gradually destabilizing cohesive faults and due to a general increase of effective stresses. Consequently, elevated average stress drop increases seismogenic index. This can lead to seismic risk increasing with the operation time of an underground reservoir.

<p>In order to evaluate the potentiality of the parameter “RST-based satellite TIR anomalies” in relation with earthquake (M≥4) occurrence, in recent years we performed three long-term statistical correlation analyses on different seismically active areas, such as Greece (Eleftheriou et al., 2016), Italy (Genzano et al., 2020), and Japan (Genzano et al., 2021).</p><p>With this aim, by means of the RST (Robust Satellite Techniques; Tramutoli, 1998, 2007) approach we analysed ten-year time series of satellite images collected by the SEVIRI sensor (on board the MSG platforms) over Greece (2004-2013) and Italy (2004-2014), and by the JAMI and IMAGER sensors (on board the MTSAT satellites) over Japan (2005-2015).  By applying empirical spatial-temporal rules, which are established also taking account of the physical models up to now proposed to explain seismic TIR anomaly appearances, the performed long -term correlation analyses put in relief that a non-casual relation exists between satellite TIR anomalies and the occurrence of earthquakes.</p><p>At the same time, in the carried out studies we introduced and validated refinements and improvements to the RST approach, which are able to minimize the proliferation of the false positives (i.e. TIR anomalies independent from the seismic sources, but due to other causes such as meteorological factors).    </p><p>Here, we summarize the achieved results and discuss them from the perspective of a multi-parameter system, which could improve our present knowledge on the earthquake-related processes and increase our capacity to assess the seismic hazard in the medium-short term (months to days).</p><p> </p><p>References</p><p>Eleftheriou, A., C. Filizzola, N. Genzano, T. Lacava, M. Lisi, R. Paciello, N. Pergola, F. Vallianatos, and V. Tramutoli (2016), Long-Term RST Analysis of Anomalous TIR Sequences in Relation with Earthquakes Occurred in Greece in the Period 2004–2013, Pure Appl. Geophys., 173(1), 285–303, doi:10.1007/s00024-015-1116-8.</p><p>Genzano, N., C. Filizzola, M. Lisi, N. Pergola, and V. Tramutoli (2020), Toward the development of a multi parametric system for a short-term assessment of the seismic hazard in Italy, Ann. Geophys, 63, 5, PA550, doi:10.4401/ag-8227.</p><p>Genzano, N., C. Filizzola, K. Hattori, N. Pergola, and V. Tramutoli (2021), Statistical correlation analysis between thermal infrared anomalies observed from MTSATs and large earthquakes occurred in Japan (2005 - 2015), Journal of Geophysics Research – Solid Earth, doi: 10.1029/2020JB020108 (accepted).</p><p>Tramutoli, V. (1998), Robust AVHRR Techniques (RAT) for Environmental Monitoring: theory and applications, in Proceedings of SPIE, vol. 3496, edited by E. Zilioli, pp. 101–113, doi: 10.1117/12.332714</p><p>Tramutoli, V. (2007), Robust Satellite Techniques (RST) for Natural and Environmental Hazards Monitoring and Mitigation: Theory and Applications, in 2007 International Workshop on the Analysis of Multi-temporal Remote Sensing Images, pp. 1–6, IEEE. doi: 10.1109/MULTITEMP.2007.4293057</p>

ABSTRACT An essential component of seismic hazard analysis is the prediction of ground shaking (and its uncertainty), using ground-motion models (GMMs). This article proposes a new method to evaluate (i.e., rank) the suitability of GMMs for modeling ground motions in a given region. The method leverages a statistical tool from sensitivity analysis to quantitatively compare predictions of a GMM with underlying observations. We demonstrate the performance of the proposed method relative to several other popular GMM ranking procedures and highlight its advantages, which include its intuitive scoring system and its ability to account for the hierarchical structure of GMMs. We use the proposed method to evaluate the applicability of several GMMs for modeling ground motions from induced earthquakes due to U.K. shale gas development. The data consist of 195 recordings at hypocentral distances (R) less than 10 km for 29 events with local magnitude (ML) greater than 0 that relate to 2018/2019 hydraulic-fracture operations at the Preston New Road shale gas site in Lancashire and 192 R<10  km recordings for 48 ML>0 events induced—within the same geologic formation—by coal mining near New Ollerton, North Nottinghamshire. We examine: (1) the Akkar, Sandikkaya, and Bommer (2014) models for European seismicity; (2) the Douglas et al. (2013) model for geothermal-induced seismicity; and (3) the Atkinson (2015) model for central and eastern North America induced seismicity. We find the Douglas et al. (2013) model to be the most suitable for almost all of the considered ground-motion intensity measures. We modify this model by recomputing its coefficients in line with the observed data, to further improve its accuracy for future analyses of the seismic hazard of interest. This study both advances the state of the art in GMM evaluation and enhances understanding of the seismic hazard related to U.K. shale gas development.