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1.
Measuring of microseismic events has been carried out at the former potash mine of Hope since early 1984.Analysis of the data demonstrates an immediate temporal relationship between brine introduction and onset of microseismic activity. The spatial distribution of the sources indicates a dependence on brine level height. Sources are found preferentially immediately next to roads and workings. Source radii, estimated from the frequency ranges in the seismograms, varied with the cross-section of neighbouring cavities and had a similar, order of size.Events occurred rarely in the previously flooded mine sections Similarly, the zone below a depth of approx. 600 m below sea level was virtually inactive. 相似文献
2.
随着地震观测台站密度的不断增加以及地震检测技术的快速发展,微震研究受到了地震学界的广泛关注。与发震周期较长的大地震相比,微震复发周期短、发生频次高,可以获得更高分辨率的地壳内部介质物性和应力状态等变化信息。微震在许多领域具有广泛的应用,如研究断层几何形态、前震与地震成核的关系、余震时空演化特征及余震触发机理、远程动态触发现象、重复地震、诱发地震以及非火山震颤信号的检测等。高精度的微震定位结果可以揭示断裂带的精细几何形态和深部活动过程,促进对断层特性和地震物理过程的深入认识。本文简要总结了国内外微震研究的主要进展,包括微震检测的主要方法和微震在多个领域的研究实例,并对微震在地震科学中的应用前景进行了展望。 相似文献
3.
Trenton T Cladouhos Susan Petty Yini Nordin Michael Moore Kyla Grasso Matt Uddenberg Michael W Swyer 《地下水科学与工程》2014,2(3):1-7
The Newberry Volcano EGS Demonstration in central Oregon tests recent technological advances designed to reduce the cost of power generated by EGS in a hot, dry well (NWG 55-29) drilled in 2008. An EGS reservoir was created by injecting large volumes of cold water, causing existing fractures to slip in shear (known as hydroshearing) generating the seismic waves that can be used to map fracture location and size. At the Newberry Demonstration the final injectivity ranged between 1.4 and 1.7 L/s/MPa a ~6x improvement over the initial injectivity of the well. The injectivity improvement and seismic analysis indicate that previously impermeable fractures were enhanced during the NWG 55-29 stimulation. 相似文献
4.
Earthquake detection probability within a seismically quiet area: application to the Bruchsal geothermal field 
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下载免费PDF全文 Emmanuel Gaucher 《Geophysical Prospecting》2016,64(2):268-286
In applications such as oil and gas production, deep geothermal energy production, underground storage, and mining, it is common practice to implement local seismic networks to monitor and to mitigate induced seismicity. For this purpose, it is crucial to determine the capability of the network to detect a seismic event of predefined magnitude in the target area. The determination of the magnitude of completeness of a network is particularly required to properly interpret seismic monitoring results. We propose a method to compute the detection probability for existing local seismic networks, which (i) strictly follows the applied detection sequence; (ii) estimates the detection capability where seismicity has not yet occurred; and (iii) delivers the results in terms of probabilities. The procedure includes a calibration of a local magnitude scale using regional earthquakes recorded by the network and located outside the monitored area. It involves pre‐processing of the seismograms recorded at each station as performed during the triggering sequence, which is assumed based on amplitude thresholds. Then, the calibrated magnitude–distance–amplitude relations are extrapolated at short distances and combined to reproduce the network detection sequence. This generates a probability to detect a seismic event of a given magnitude at a specified location. This observation‐based approach is an alternative to a fully theoretical detection capability modelling and includes field conditions. Seismic wave attenuation by geometrical spreading and intrinsic attenuation, site effect, and instrumental responses are partly accounted for by the calibration. We apply this procedure on the seismic network deployed in the Bruchsal geothermal field (Germany). Although the system was in good working order, no induced seismicity was identified in the area between June 2010, when monitoring started, and November 2012. The recording of distant seismicity during this time period, however, allowed the application of the proposed procedure. According to the applied network detection parameters, the results indicate that the absence of seismicity can be interpreted as a 95% probability that no seismic event with ML ≥ 0.7 occurred below the network at 2.4‐km depth, i.e., in the geothermal reservoir. 相似文献
5.
微地震震源机制的反演对于非常规油气开发具有至关重要的作用.微地震信号主频高、能量小,容易受地层吸收衰减作用的影响使其波形发生畸变,本文提出了一种考虑地层吸收衰减作用的微震源机制反演方法,并利用费雷谢偏导矩阵的SVD分解(特征值分解)方法,分析研究了地层的吸收衰减因子的变化对于微地震震源机制反演分辨率的影响,根据理论计算给出了不同地震数据对各种震源机制反演的适用条件.理论计算证明,采用直达P波和S波数据联合反演震源的T值,单独利用直达P波反演震源的k值,可以有效降低地层吸收衰减作用对反演结果的影响. 相似文献
6.
利用近代微震资料研究地震危险性 总被引：1，自引：0，他引：1
利用１９７０～１９９３年华北地区ＭＬ≥２．０的微震资料，根据其地震活动特点，从中挑选了一些有代表性的区域，做其Ｇ－Ｒ关系曲线，由该曲线可得到每个震级的年频次，同时，由该区域的历史地震（１３００－１９９３年）可得到较大震级的实际年频次，两者对比，发现具有很好的一致性。因此，当选取合适的区域时，利用近代微资料可以推测出该区域较大地震的活动情况，但同时有两点注意：（１）利用微震资料进行统计时，得到的得一 相似文献
7.
Source parameter scaling relations are examined for microseismic events (–2.4M–0.3) occurring within higyly and moderately stressed and fractured rock masses at Strathcona mine, Sudbury, Canada. Insight into scaling is provided by waveform complexities, calculated rupture velocities, and maximum shear stresses based onin situ and numerical modelling data. The importance of normal stress on the failure process is also considered. Our results show that a strong dependence exists between stress release and seismic moment. An observed positive scaling in excess stress release (/2–
a
) is consistent with the concept of overshoot. Rupture velocities ranging from 0.2 to 0.5 and waveform complexities less than 1.5 suggested that overshoot was related to healing behind a slowly advancing rupture front. Scaling in seismic efficiency paralleled that in apparent stress, implying that seismic stress release estimates are quasi-independent of the maximum shear stress. High levels of normal stress further supported the importance of high resisting stress in the observed overshoot behaviour and its role in the failure process. 相似文献
8.
We provide an overview of the current status of seismic monitoring instrumentation employed in Canadian underground mines. Based on several case studies, we outline how passive seismic monitoring techniques are being used to evaluate fractures and stress conditions associated with ore extraction at depth. It is shown that induced microseismicity allows for the remote monitoring of active fractures, delineating modes of failure with advancing excavation fronts, and identifying variations in principal stress orientations during sequential stages of mining. Advances into the characterization of excavation zone of influence through deformation state analysis and the use of seismic hazard analysis to evaluate the potential for ground instability are also discussed. 相似文献
9.
Yang Zhang Leo Eisner William Barker Michael C. Mueller Kevin L. Smith 《Geophysical Prospecting》2013,61(5):919-930
We develop a methodology to obtain a consistent velocity model from calibration shots or microseismicity observed on a buried array. Using a layered 1D isotropic model derived from checkshots as an initial velocity model, we invert P‐wave arrival times to obtain effective anisotropic parameters with a vertical axis of symmetry (VTI). The nonlinear inversion uses iteration between linearized inversion for anisotropic parameters and origin times or depths, which is specific to microseismic monitoring. We apply this technique to multiple microseismic events from several treatments within a buried array. The joint inversion of selected events shows a largely reduced RMS error indicating that we can obtain robust estimates of anisotropic parameters, however we do not show improved source locations. For joint inversion of multiple microseismic events we obtained Thomsen anisotropic parameters ε of 0.15 and δ of 0.05, which are consistent with values observed in active seismic surveys. These values allow us to locate microseismic events from multiple hydraulic fracture treatments separated across thousands of metres with a single velocity model. As a result, we invert the effective anisotropy for the buried array region and are able to provide a more consistent microseismicity mapping for past and future hydraulic fracture stimulations. 相似文献
10.
Back‐projection stacking of P‐ and S‐waves to determine location and focal mechanism of microseismic events recorded by a surface array 下载免费PDF全文
下载免费PDF全文 We present an automatic method of processing microseismic data acquired at the surface by a star‐like array. The back‐projection approach allows successive determination of the hypocenter position of each event and of its focal mechanisms. One‐component vertical geophone groups and three‐component accelerometers are employed to monitor both P‐ and S‐waves. Hypocenter coordinates are determined in a grid by back‐projection stacking of the short‐time‐average‐to‐long‐time‐average ratio of absolute amplitudes at vertical components and polarization norm derived from horizontal components of the P‐ and S‐waves, respectively. To make the location process more efficient, calculation is started with a coarse grid and zoomed to the optimum hypocenter using an oct‐tree algorithm. The focal mechanism is then determined by stacking the vertical component seismograms corrected for the theoretical P‐wave polarity of the focal mechanism. The mechanism is resolved in the coordinate space of strike, dip, and rake angles. The method is tested on 34 selected events of a dataset of hydraulic fracture monitoring of a shale gas play in North America. It was found that, by including S‐waves, the vertical accuracy of locations improved by a factor of two and is equal to approximately the horizontal location error. A twofold enhancement of horizontal location accuracy is achieved if a denser array of geophone groups is used instead of the sparse array of three‐component seismometers. The determined focal mechanisms are similar to those obtained by other methods applied to the same dataset. 相似文献