Macroseismic formula for determining hypocentral depth and its precise calculative method

ＭａｃｒｏｓｅｉｓｍｉｃｆｏｒｍｕｌａｆｏｒｄｅｔｅｒｍｉｎｉｎｇｈｙｐｏｃｅｎｔｒａｌｄｅｐｔｈａｎｄｉｔｓｐｒｅｃｉｓｅｃａｌｃｕｌａｔｉｖｅｍｅｔｈｏｄＸＩＮＧＢＥＩＤＵＡＮ（段星北）４ＥｎｔｒａｎｃｅｔｏＮｏ．１１０ｏｆＢｕｉｌｄｉｎｇ...     

Contributors to this issue

Ｇｕｏ－ＭｉｎＺＨＡＮＧ（张国民）ＧｏｔＢａｃｈｅｌｏｒａｎｄＭａｓｔｅｒＤｅｇｒｅｅｓｉｎＧｅｏｐｈｙｓｉｃａｌＤｅｐａｒｔｍｅｎｔ，ｔｈｅＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙＵｎｉｖｅｒｓｉｔｙ．ｏｆＣｈｉｎａｉｎ１９６５ａｎｄ１９６８ｒｅｓ...     

Method of expected earthquake losses estimation based on the frequency of seismic site intensity

Ｍｅｔｈｏｄｏｆｅｘｐｅｃｔｅｄｅａｒｔｈｑｕａｋｅｌｏｓｓｅｓｅｓｔｉｍａｔｉｏｎｂａｓｅｄｏｎｔｈｅｆｒｅｑｕｅｎｃｙｏｆｓｅｉｓｍｉｃｓｉｔｅｉｎｔｅｎｓｉｔｙ高孟潭Ｍｅｎｇ－ＴａｎＧＡＯ（ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ,Ｓｔａｔｅ...     

Parameter sensitivity analyses in seismic hazard

Ｐａｒａｍｅｔｅｒｓｅｎｓｉｔｉｖｉｔｙａｎａｌｙｓｅｓｉｎｓｅｉｓｍｉｃｈａｚ┐ａｒｄＪＩＡＮＷＡＮＧ（王健）ａｎｄＭＥＮＧ－ＴＡＮＧＡＯ（高孟潭）ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，ＳｔａｔｅＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕ，Ｂｅ...     

SOME APPROACHES FOR STUDYING THE INTENSITY OF SMALL RIVER AGGRADATION

ＳＯＭＥＡＰＰＲＯＡＣＨＥＳＦＯＲＳＴＵＤＹＩＮＧＴＨＥＩＮＴＥＮＳＩＴＹＯＦＳＭＡＬＬＲＩＶＥＲＡＧＧＲＡＤＡＴＩＯＮＶ．Ｎ．Ｇｏｌｏｓｏｖ（ＬａｂｏｒａｔｏｒｙｏｆＳｏｉｌａｎｄＦｌｕｖｉａｌＰｒｏｃｅｓｓｅｓ，ＦａｃｕｌｔｙｏｆＧｅｏｇｒａｐｈ...     

《ActaSeismologicaSinica》isinprogress──reporttothefourthsessionofacademicsymposlumofSSContheworkofASS（1992－1994）

《ＡｃｔａＳｅｉｓｍｏｌｏｇｉｃａＳｉｎｉｃａ》ｉｓｉｎｐｒｏｇｒｅｓｓ──ｒｅｐｏｒｔｔｏｔｈｅｆｏｕｒｔｈｓｅｓｓｉｏｎｏｆａｃａｄｅｍｉｃｓｙｍｐｏｓｌｕｍｏｆＳＳＣｏｎｔｈｅｗｏｒｋｏｆＡＳＳ（１９９２－１９９４）Ｘｉｎ－ＭｅｉＬＩＵａｎｄＹ...     

Grouping occurrences being the fundamental feature of the strong earthquakes in Chinese mainland

ＧｒｏｕｐｉｎｇｏｃｃｕｒｒｅｎｃｅｓｂｅｉｎｇｔｈｅｆｕｎｄａｍｅｎｔａｌｆｅａｔｕｒｅｏｆｔｈｅｓｔｒｏｎｇｅａｒｔｈｑｕａｋｅｓｉｎＣｈｉｎｅｓｅｍａｉｎｌａｎｄＱｉｎ－ＺｕＬＩ（李钦祖）；Ｌｉ－ＭｉｎＹＵ（于利民）；Ｊｉ－ＹｉＷＡＮＧ（王吉易...     

The relationship between crust-mantle structural ratio and seismic activity

（毛桐恩，姚家榴）Ｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｃｒｕｓｔ－ｍａｎｔｌｅｓｔｒｕｃｔｕｒａｌｒａｔｉｏａｎｄｓｅｉｓｍｉｃａｃｔｉｖｉｔｙ￥Ｔｏｎｇ－ＥｎＭＡＯａｎｄＪｉａ－ＬｉｕＹＡＯ（ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，Ｓｔ...     

The fracture characteristic of the 1989 Datong-Yanggao earthquake sequence

Ｔｈｅｆｒａｃｔｕｒｅｃｈａｒａｃｔｅｒｉｓｔｉｃｏｆｔｈｅ１９８９Ｄａｔｏｎｇ－ＹａｎｇｇａｏｅａｒｔｈｑｕａｋｅｓｅｑｕｅｎｃｅＳｉ－ＣｈａｎｇＺＨＡＮＧ（张四昌），Ｇｕｉ－ＬｉｎｇＤＩＡＯ（刁桂苓）ａｎｄＬｉ－ＭｉｎＹＵ（于利民）（Ｓｅｆｒｍｏ...     

Measurement of radon gas on major faults in California,USA

ＭｅａｓｕｒｅｍｅｎｔｏｆｒａｄｏｎｇａｓｏｎｍａｊｏｒｆａｕｌｔｓｉｎＣａｌｉｆｏｒｎｉａ，ＵＳＡＷｅｉＺＨＡＮＧ（张炜）ａｎｄＣｈｉ－ＹｕＫＩＮＧ（金继宇）（ＣｅｎｔｅｒｆｏｒＡｎａｌｙｓｉｓａｎｄＰｒｅｄｉｃｔｉｏｎ，ＳｔａｔｅＳｅｓｉｍｏｌｏ...     

Fluid-induced seismicity: Pressure diffusion and hydraulic fracturing

Borehole fluid injections are common for the development of hydrocarbon and geothermic reservoirs. Often they induce numerous microearthquakes. Spatio-temporal dynamics of such induced microseismic clouds can be used to characterize reservoirs. However, a fluid-induced seismicity can be caused by a wide range of processes. Here we show that linear pore pressure relaxation and a hydraulic fracturing are two asymptotic end members of a set of non-linear diffusional phenomena responsible for seismicity triggering. To account for the whole range of processes we propose a rather general non-linear diffusional equation describing the pore pressure evolution. This equation takes into account a possibly strong enhancement of the medium permeability. Both linear pore pressure relaxation and hydraulic fracturing can be obtained as special limiting cases of this equation. From this equation we derive the triggering front of fluid induced seismicity, which is valid in the general case of non-linear pore pressure diffusion. We demonstrate corresponding seismicity signatures on different case studies.     

微地震方法的裂缝监测与储层评价

在油田水力压裂微地震事件定位结果的基础上,结合有效微地震事件的时空分布、震级大小、地震矩、震源半径、应力降和b值等地震学参数进行综合研究,并结合研究区域的地质背景和测井资料对水力压裂诱发的裂缝网络进行几何形态分析和应力解释.本文提出的微地震综合分析解释方法可对压裂后储层物性进行综合评价,有利于对储层改造效果进行预测,对油田的水力压裂施工具有指导意义.     

Interpretation of Microseismicity Resulting from Gel and Water Fracturing of Tight Gas Reservoirs

We provide a comparative analysis of the spatio-temporal dynamics of hydraulic fracturing-induced microseismicity resulting from gel and water treatments. We show that the growth of a hydraulic fracture and its corresponding microseismic event cloud can be described by a model which combines geometry- and diffusion-controlled processes. It allows estimation of important parameters of fracture and reservoir from microseismic data, and contributes to a better understanding of related physical processes. We further develop an approach based on this model and apply it to data from hydraulic fracturing experiments in the Cotton Valley tight gas reservoir. The treatments were performed with different parameters such as the type of treatment fluid, the injection flow rate, the total volume of fluid and of proppant. In case of a gel-based fracturing, the spatio-temporal evolution of induced microseismicity shows signatures of fracture volume growth, fracturing fluid loss, as well as diffusion of the injection pressure. In contrast, in a water-based fracturing the volume creation growth and the diffusion controlled growth are not clearly separated from each other in the space-time diagram of the induced event cloud. Still, using the approach presented here, the interpretation of induced seismicity for the gel and the water treatments resulted in similar estimates of geometrical characteristics of the fractures and hydraulic properties of the reservoir. The observed difference in the permeability of the particular hydraulic fractures is probably caused by the different volume of pumped proppant.     

Optimum size and density of surface grid arrays for retrieving accurate shear-tensile fracturing of microearthquakes

Surface arrays became an important tool for monitoring the induced seismicity in hydraulic fracturing experiments and for assessing the impact of fluid injection on the fracturing process of microearthquakes. The layout of sensors plays a key role in this task because it controls the accuracy of event locations and retrieved seismic moment tensors. We simulate various configurations of grid sensor arrays characterized by a different number of sensors, array span, sensor spacing, depth of sources and various shear/tensile source mechanisms of events. The moment tensor inversion is carried out using synthetically calculated P-wave amplitudes with added random noise. A bias in the solutions is evaluated by errors in the double-couple percentage of inverted moment tensors because the double-couple errors inform us about the sensitivity of the network to detect the shear/tensile fracturing mode of induced microearthquakes. The results show that the accuracy of the double-couple percentage is mostly controlled by the offset-to-depth ratio R defined as the ratio of half of the network size to the event depth. The optimum value of R is in the range of 0.75–1.5 irrespective of the type of the focal mechanism. If 121 (11 × 11) sensors are distributed in a regular grid and recorded data are characterized by a 10% random noise, the double-couple error is less than 6%. This error increases, if R is not optimum or if the number of sensors is reduced. However, even sparse arrays with 49 (7 × 7) or 16 (4 × 4) sensors can yield a reasonable accuracy, provided the surface grid arrays are designed to have an optimum size.     

全球油气开采诱发地震的研究现状与对策

人工诱发地震现象已经有很久的历史.水库蓄水、采矿、地热开发、从地下提取液体或气体,或将液体注入地球内部都可能诱发地震.大量地震监测数据与科学分析结果显示:美国俄克拉何马州的地震剧增主要与页岩油气开采的废水回注量相关;加拿大阿尔伯塔省的地震剧增主要与页岩油气开采水力压裂的工作量相关;而荷兰罗宁根天然气田的传统天然气开采也同样诱发了较强的地震活动.在中国四川盆地的页岩油气开发区域,地震活动近几年也大幅度增强,但目前监测与科研工作较少,对某些地震成因尚有争议.目前研究诱发地震问题已成为学术界与工业界的一门专业学科.推断诱发地震,除了分析时空分布与工业活动的相关性之外,本文综述了该领域基于地震学、地质动力学、构造地质学的多种分析方法.如何在油气开采过程中减少诱发地震的灾害影响成为当前相关各界极为关注的科研问题,本文介绍了多个国家或地区建立的控制诱发地震的管理系统、基于地震大数据的诱发地震概率预测方法,以及基于地球物理与地质信息的综合诱发地震风险评估方法,并对我国控制诱发地震问题提出建设性意见.     

基于“剪切+张裂”一般位错模型频率域求解微震震源机制

研究微地震的震源机制,获得压裂区域的破裂方向、尺度和应力状态等信息,在非常规油气开采过程中具有重要意义.对于微震,通常采用剪切位错或者矩张量模型对震源进行描述.本文从其实际发震机制出发,使用了"剪切+张裂"的一般位错点源模型,并基于此模型发展了一种利用全波形信息,通过波形振幅谱相关和初至约束,在频率域求解微震震源机制的方法.该方法适用于地面和井中观测,能够在得到常规震源参数（断层走向、倾角和滑动角）的同时给出裂缝断层剪切和张裂错动的距离信息,更直观体现破裂程度.理论数值测试证明方法有效、可行,在未滤波的情况下,实际数据的波形拟和结果仍较为一致,同时还发现错动距离与应力降等常规破裂参数并不严格相关,说明剪切、张裂错距可作为独立的新参数来定量评估水压致裂效果,指导工程开发进行.     

油气田典型岩石三轴压缩变形破坏与声发射活动特征——四川盆地震旦系白云岩及页岩的破坏过程

随着二氧化碳地质封存、深部地热开采、地下储气库建设、页岩气开发、二次驱油/驱气等工业应用的快速发展,与地下流体注入有关的诱发地震活动呈现一定的增加趋势.利用声发射实验观测油气田典型岩石在三轴压缩条件下变形破坏过程与声发射活动特征,对研究注水诱发地震过程有着重要意义.本文利用四川盆地现场采集的震旦系白云岩及页岩,采用实验室声发射技术观测研究岩石三轴压缩变形破坏过程中地震波速度等物性参数及声发射事件时空分布特征.实验结果表明:震旦系白云岩及页岩在变形破坏过程中均有一定的声发射活动.根据声发射定位结果,声发射主要集中在破坏前后的较短时间内,页岩的层理面为结构弱面,控制最终破坏面的形态及声发射特征.根据应力-应变结果,白云岩在压缩的后期阶段有一定的扩容现象,但页岩在整个压缩阶段均没有明显扩容现象.研究结果表明四川盆地较古老的白云岩及页岩具有脆性破坏特征,地下流体注入容易诱发微震活动,形成裂缝,有利于页岩气压裂开采.微震活动有利于监测裂缝的发生发展,但同时在页岩气开发及二氧化碳地质封存时应采取相应的预防控制措施进行安全合理的储盖层管理,避免灾害性诱发地震的发生.     

Location of microearthquakes sources at passive seismic monitoring of hydraulic fracturing

The paper discusses microseismic monitoring during oil well stimulation by hydraulic fracturing, an emergent technology used for hydraulic fracturing layer control. The passive monitoring is a new widely developing technology of HFL control. The main factor affecting the results of passive seismic monitoring is the event location accuracy. The passive monitoring acquisition system utilizes one three components seismic probe deployed into the observation well. To evaluate the location accuracy of induced events for one observation well we applied traditional kinematic approach based on picking of earthquake P- and S-waves arrivals. The influence of geometric parameters of geophones location in a borehole, their quantity, picking errors of waves arrivals on the accuracy of microearthquakes location is studied.     

Seismological Studies of a Fluid Injection in Sedimentary Rocks, East Texas

—?Induced microseismicity data from a large volume fluid injection into sedimentary rock was analyzed to study the fracture system, fluid pathways, and state of stress in the lower Frio formation in east Texas. Seismicity data are from two arrays of 25 3-component geophone packages sited in two monitoring boreholes. From a total of 2,894 event triggers, a subset of 54 microearthquakes was chosen for their high quality seismograms and clear P and S arrivals. Arrival times were picked with a precision of 0.5 to 1.0?ms, and microearthquakes were located with hypocentral uncertainties estimated as less than 10–20?m. Hypocenters farthest from the injection well define a nearly horizontal tube of seismicity approximately aligned in the direction of the injection well. A simultaneous inversion of arrival times for transverse isotropic velocity structure and hypocenters yielded P-wave anisotropy of ?14% and S-wave anisotropy of ?2%. Thus, velocities along vertical ray paths are higher than those along horizontal paths, probably because of lithologic differences. Single-event focal mechanisms were determined for 47 events, and many of them are normal fault type. The minimum principal stress derived from the focal mechanisms is nearly horizontal and trends approximately north-south, consistent with the regional stress state. An imaging analysis of the seismograms shows the presence of strong seismic scatterers at positions that correlate with boundaries seen in the hypocenters; both features probably result from a similar set of heterogeneities. This study demonstrates the abundance of information that can be extracted from induced seismicity data and underscores the value of induced seismicity monitoring for studying the fluid and fracture systems created by fluid injections.     

Fracture Toughness Evaluation Based on Tension-softening Model and its Application to Hydraulic Fracturing

This paper discusses the applicability of the tension-softening model in the determination of the fracture toughness of rocks, where the fracture toughness evaluated based on the tension-softening model is compared with the crack growth resistance deduced from laboratory-scale hydraulic fracturing tests. It is generally accepted that the fracture process is dominated by the growth of a fracture process zone for most types of rocks. In this study, the J-integral based technique is employed to determine the fracture toughness of Iidate granite on the basis of the tension-softening model, where compact tension specimens of different dimensions were tested in order to examine the specimen size effect on the measured fracture toughness. It was shown that the tension-softening relation deduced from the J-integral based technique allowed us to determine the specimen size independent fracture toughness K_c of Iidate granite. Laboratory-scale hydraulic fracturing tests were performed on cubic specimens (up to a 10 m sized specimen), where cyclic pressurization was conducted using a rubber-made straddle packer to observe the extent of the hydraulically induced crack. The experimental results of pressure and crack length were then used to construct the crack growth resistance curve based on the stress intensity factor K. The crack growth resistance obtained from the hydraulic fracturing tests was observed to initially increase and then level off, giving a constant K value for a long crack extension stage. The plateau K value in the crack growth resistance curve was found to be in reasonable agreement with the fracture toughness K_c deduced from the tension-softening relation. It was demonstrated that the tension-softening model provides a useful tool to determine the appropriate fracture toughness of rocks, which may be applicable for the analysis of the process of large-scale crack extension in rock masses.