Spatial-temporal evolution of gas migration pathways in coal during shear loading

Custom designed and built meso shear test equipment was used to examine the shear crack propagation in gassy coal under different gas pressures.The spatial-temporal evolution of gas migration pathways in the coal during shear loading was also researched.The results show that gas pressure can hasten crack growth at the shear fracture surface,can reduce the shear strength of gassy coal,and can accelerate the shear failure process.Shear failure in gassy coal exhibits five stages:the pre-crack stage;the stable crack growth stage;the unsteady crack growth stage;the fracture stage;and,finally,the friction crack stage.The shear breaking creates two kinds of crack,shear cracks and tensile cracks.Cracks first appear in the shear plane at both ends and then extend toward the center until a shear fracture surface forms.The direction of shear crack propagation diverges from the predetermined shear plane by an angle of about 5°-10°.

The Statistical Analysis of Migration of Strong Earthquakes─Taking the North China Region as an Example

The migration of strong earthquakes is an important research topic because the migration phenomena reflect partly the seismic mechanism and involve the prediction of tendency of seismic activity. Research on migration of strong earthquakes has mostly focused on finding the phenomena. Some attempts on getting regularity were comparatively subjective. This paper suggests that there should be indices of migration in earthquake dataset and the indexes should have statistical meaning if there is regularity in the migration of strong earthquakes. In this study, three derivative attributes of migration, i.e., migration orientation, migration distance and migration time interval, were statistically analyzed. Results in the North China region show that the migration of strong earthquakes has statistical meaning. There is a dominant migration orientation (W by S to E by N), a dominant distance (≤100km and on the confines of 300～700km), and a dominant time interval (≤1a and on the confines of 3～4a). The results also show that the migration will differ slightly with different magnitude range or earthquake activity phase.

The Migration Characteristics of Strong Earthquakes on the North-South Seismic Belt and Its Relation with the South Asia Seismic Belt

Migration of strong earthquakes (M≥7.0) along the North-South Seismic Belt of China since 1500 AD shows three patterns: Approximately equal time and distance interval migration from N to S, varied patterns of migration from S to N and grouped strong earthquake activity in a certain period over the entire seismic belt. Analysis of strong earthquakes in the past hundred years shows that the seismicity on the North-South Seismic Belt is also associated with strong earthquake activities on the South Asia Seismic Belt which extends from Myanmar to Sumatra, Indonesia. Strong earthquakes on the former belt often lag several months or years behind the quakes occurring on the later belt. So, after the occurrence of the December 26, 2004 M_S8.7 great earthquake off the western coast of Sumatra, Indonesia, the possibility of occurrence of strong earthquakes on the North-South Seismic Belt of China cannot be ignored. The above-mentioned migration characteristics of strong earthquakes are related to the northeastward collision and subduction of the India Plate as well as the interaction between the Qinghai-Xizang (Tibet) Plateau and the stable and hard Ordos and Alashan Massifs at its northeastern margin.

High-resolution seismicity imaging and early aftershock migration of the 2023 Kahramanmara?(SE Türkiye)M_W7.9&7.8 earthquake doublet

We build a high-resolution early aftershock catalog for the 2023 SE Türkiye seismic sequence with PALM,a seamless workflow that sequentially performs phase picking,association,location,and matched filter for continuous data.The catalog contains 29,519 well-located events in the two mainshocks rupture region during 2023-02-01–2023-02-28,which significantly improves the detection completeness and relocation precision compared to the public routine catalog.Employing the new PALM catalog,we analyze the structure of the seismogenic fault system.We find that the Eastern Anatolian Fault(EAF)that generated the first M_(W)7.9 mainshock is overall near-vertical,whereas complexities are revealed in a small-scale,such as subparallel subfaults,unmapped branches,and stepovers.The seismicity on EAF is shallow(<15 km)and concentrated in depth distribution,indicating a clear lock-creep transition.In contrast,the SürgüFault(SF)that is responsible for the second M_(W)7.8 mainshock is shovel-shaped for the nucleation segment and has overall low dip angles(~40°–80°).Aftershocks on the SF distribute in a broad range of depth,extending down to~35 km.We also analyze the temporal behavior of seismicity,discovering no immediate foreshocks within~5 days preceding the first mainshock,and no seismic activity on the SF before the second mainshock.

Spatial-temporal Distribution Characteristics of Global Seismic Clusters and Associated Spatial Factors

Earthquakes exhibit clear clustering on the earth. It is important to explore the spatial-temporal characteristics of seismicity clusters and their spatial heterogeneity. We analyze effects of plate space, tectonic style, and their interaction on characteristic of cluster.Based on data of earthquakes not less than moment magnitude(M_w) 5.6 from 1960 to 2014, this study used the spatial-temporal scan method to identify earthquake clusters. The results indicate that seismic spatial-temporal clusters can be classified into two types based on duration: persistent clusters and burst clusters. Finally, we analysed the spatial heterogeneity of the two types. The main conclusions are as follows: 1) Ninety percent of the persistent clusters last for 22-38 yr and show a high clustering likelihood;ninety percent of the burst clusters last for 1-1.78 yr and show a high relative risk. 2) The persistent clusters are mainly distributed in interplate zones, especially along the western margin of the Pacific Ocean. The burst clusters are distributed in both intraplate and interplate zones, slightly concentrated in the India-Eurasia interaction zone. 3) For the persistent type, plate interaction plays an important role in the distribution of the clusters’ likelihood and relative risk. In addition, the tectonic style further enhances the spatial heterogeneity. 4) For the burst type,neither plate activity nor tectonic style has an obvious effect on the distribution of the clusters’ likelihood and relative risk. Nevertheless,interaction between these two spatial factors enhances the spatial heterogeneity, especially in terms of relative risk.

Temporal variation of gravity field prior to the Ludian Ms6.5 and Kangding Ms6.3 earthquakes

Using mobile gravity data from the central area of Sichuan and Yunnan Provinces, the relationship between gravity variation and earthquakes was studied based on the Ludian Ms6.5 earthquake that occurred on August 3rd, 2014, and the Kangding Ms6.3 earthquake that occurred on November 22 nd, 2014; the mechanism of gravity variation was also explored. The results are as follows：（1） Prior to both earthquakes, gravity variation exhibited similar characteristics as those observed before both the Tangshan and Wenchuan earthquakes, in which typical precursor anomalies were positive gravity variation near the epicenter and the occurrence of a high-gravity-gradient zone across the epicenter prior to the earthquake.（2） A relatively accurate prediction of the occurrence locations of the two earthquakes was made by the Gravity Network Center of China（GNCC） based on these precursor anomalies. In the gravity study report on the 2014 earthquake trends submitted at the end of 2013, the Daofu-Shimian section at the junction of the Xianshuihe and Longmenshan fault zones was noted as an earthquake-risk region with a predicted magnitude of 6.5, which covered the epicenter of the Kangding Ms6.3 earthquake. In another report on earthquake trends in southwestern China submitted in mid-2014, the Lianfeng, Zhaotong fault zone was also classified as an earthquake-risk region with a magnitude of 6.0, and the central area of this region basically overlapped with the epicenter of the Ludian Ms6.5 earthquake.（3） The gravity variation characteristics are reasonably consistent with crustal movements, and deep material migration is likely the primary cause of gravity variation.

Some Mass Migration Underground Found in Beijing Area

The relationship between the change of a local gravity field and the mass migration underground is discussed by means of using a point-source disturbed body as a substitute for the mass migration underground. Some significant local gravity field changes in Beijing area have been found, from which the three parameters of the disturbed bodies, location, depth and mass, have been derived successfully from the observations of a gravimetric network. In order to determine the depth of a body, a new approach is suggested in which the gravity change difference is used instead of the gravity change itself. The mass of a disturbing body has been estimated properly. Astronomical PZT is suggested for this kind of survey. The results provide us a picture of the underground mass migration with which the gravity changes on the ground surface may be interpreted in a better way. This additional information may be useful in seismological studies.

Dynamic Evolution of Precursory Field and Its Relation With the Group of Strong Earthquakes

Spatial scanning is done for two regions in Chinese Mainland,where displayed a denseprecursory network during 1994～1998.The two regions are the mid-southern segment of theNorth-south seismic belt(20°～35°N,95°～110°E)and North China(36°～42°N,110°～120°E).We took 0.5°×0.5°as a spatial window with a step of 0.25°and 4 months as atemporal window with a step of 1 month.For the two regions,the anomaly density is scannedfrom 1994 and 1995 respectively in the two regions.The precursory anomalies are all fromthe Division of Seismic Trend in China and the Division of Seismic Trend in the Capital Area,Center for Analysis and Prediction,China Seismological Bureau.A seismogenic tectonicmodel is introduced to explain the scanning results.In the model,the frictional strength ofthe focal sources is distributed randomly.After the boundary plate motion rate and all othergeological parameters are given,the stress of the sources in the system changesinhomogenously due to the variation of the frictional

Spatial-temporal patterns of China＇s interprovincial migration, 1985-2010

Migration plays an increasing role in China＇s economy since mobility rose and economic restructuring has proceeded during the last three decades. Given the background of most studies focusing on migration in a particular period, there is a critical need to analyze the spatial-temporal patterns of migration. Using bicomponent trend mapping technique and interprovincial migration data during the periods 1985-1990, 1990-1995, 1995-2000, 2000- 2005, and 2005-2010 we analyze net-, in-, out-migration intensity, and their changes over time in this study. Strong spatial variations in migration intensity were found in China＇s interprovincial migration, and substantial increase in migration intensity was also detected in eastern China during 1985-2010. Eight key destinations are mostly located within the three rapidly growing economic zones of eastern China （Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei Metropolitan Region）, and they are classified into three types： mature, emerging, and fluctuant origins, while most key origins are relatively undeveloped central and western provinces, which are exactly in accordance with China＇s economic development patterns. The results of bicomponent trend mapping indicate that, in a sense, the migration in the south was more active than the north over the last three decades. The result shows the new changing features of spatial-temporal patterns of China＇s interprovincial migration that Fan and Chen did not find out in their research. A series of social-economic changes including rural transformation, balanced regional development, and labor market changes should be paid more attention to explore China＇s future interprovincial migration.

Lagrangian-based spatial-temporal topological study on the evolution and migration of coherent structures in wall turbulence

In this work,we study the development,evolution,and migration of turbulent coherent structures in the turbulent boundary layer at Reτ=630 using time-resolved particle image velocimetry(TR-PIV).Multiple techniques,including multi-scale analysis,conditional averaging,cross-correlation,and spatial-temporal topological analysis are applied to extract the evolution principle,migration trajectory,and convection velocity vector of the targeted coherent structures from a Lagrangian perspective.The spanwise vortex structures with larger scale and intensity at a certain wall-normal height y were the main focus of the present study.In the statistical sense,spanwise vortex structures move away from the wall with the shape changing from a bulge to an ellipse,and finally to a circle.Two straight lines emerge from the mean transfer trajectory curve of the spanwise vortex,in which the horizontal one is located at the viscous sublayer(y^(+)<10),the other is a logarithmic straight line existing in the range of 50<y^(+)<120,and the inclination angle of the tangential migration path is fixed at around 12°.The streamwise convection velocity U_(c)of scaled spanwise vortex structures satisfies U_(c)/U_(∞)=0.5-0.6 below y=0.03δ(i.e.,U^(+)_(c)=11-13 undery^(+)=20).In particular,in the region of 50<y^(+)<120,the velocity growth curves of U_(c)and wall-normal convection velocity V_(c)follow the log-law distribution very well,and the slopes are consistent with that of the log-law region of the turbulent boundary layer.Our observations provide microscopic evidences of the logarithmic-linear distribution of the migration trajectory of spanwise vortex structures.

The Datong earthquake and its anomalous tilt Field

In this paper, the similarity and the meanings of anomalous pattern of entropy for tilt tide amplitude factor, the distribution of entropy and dimension for tilt velocity, the similarity and relationships for long-period tilt deformation and earthquake migration are demonstrated. The deformation wave and its meanings have also been explained. The authors explored the relationships between distribution of similar pattern and epicenter. The possibility of prediction for next earthquake epicenter has also been explored based on the combining tilt field and earthquake activity.

Rupture pattern of the Oct 23,2011 Van-Merkez,Eastern Turkey earthquake

High-frequency rupture process of the Oct 23, 2011 Van-Merkez earthquake is imaged by back-projection method using high-quality teleseismic P wave data from the US Array, and prestack Kirchhoff migration using P wave data from a subarray of global seismic networks. The rupture model with two asperities is confirmed by previous two methods. In low-frequency imaging, a large asperity derived from the migration method corresponds to the second one from the high-frequency P waves. The con- sistency of the locations of asperities from datasets with different frequency bands indicates that there is possible insignificance of the frequency-dependent feature for the earthquake. The resultant images illustrate the spatial and temporal evolution of the rupture, which mainly propa- gated WSW over a length of 33 km during the first 18 s, accompanying with bursts of two asperities at 3 and 11-13 s. The rupture direction is confirmed by the S wave comer frequency variations of strong ground accelerations. The rupture fronts are mainly located at the updip of the causative fault. Based on polarities of the P waveforms and focal mechanisms of the mainshock and aftershocks, the failure of these two asperities is determined to have occurred on a reverse fault with a dip angle of 47°. Hence, the rupture pattern of the 2011 Van-Merkez earthquakewas dominated by a unilateral rupture toward the west- southwest direction.

Propagation of crust deformation anomalies related to the Menyuan M_(S) 6.9 earthquake

Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research. In this paper, the temporal and spatial distribution characteristics of deformation anomalies in the northeastern margin of the Qinghai-Tibetan Plateau before and after the Menyuan M_(S)6.9 earthquake were studied by using the Fisher statistical test method. By analyzing the characteristics of these anomalies, we found that: 1) The deformation anomalies are mainly distributed in the marginal front area of the Qinghai-Tibetan Plateau, where short-term deformation anomalies are prone to occur due to a high gradient of gravity;2) The deformation anomalies along the northeastern margin of the Qinghai-Tibetan Plateau are characterized by spatial propagation, and the migration rate is about 2.4 km/d. The propagation pattern is counterclockwise, consistent with the migration direction of M_(S)≥ 6.0 earthquakes;3) The time and location of the Menyuan earthquake are related to the group migration of earthquakes with M_(S)≥ 6.0. Finally,based on the results of gravity field variation and the theory of crust stress wave, the law of deformation anomaly distribution was discussed. We suggest that both the deformation propagation along the northeastern margin of the Qinghai-Tibetan Plateau and the earthquake migration are possibly associated with the variation of the stress field caused by subsurface mass flow.

A Preliminary Analysis of Seismotectonics for the Indonesia M8.7 Earthquake on December 26, 2004

The Indonesian region is one of the most seismically active zones on the earth. On December 26, 2004, an M_S 8.7 earthquake (as measured by the China Seismograph Network, or M_w = 9.3 as measured by USGS) struck the west coast of northern Sumatra, Indonesia. By its magnitude it is classified as the world’s fourth largest earthquake since 1900 and the largest one since the 1964 Alaska earthquake. The spatial distribution of the relocation of larger aftershocks (M>4.5) following the main shock suggests a length and width of the rupture of about 1200km and 200km, respectively. The shock triggered massive tsunamis that affected several countries throughout South and Southeast Asia. It is a shallow interplate event of thrust type in the trench. Its epicenter is located at the northwestern end of the Indonesia-Melanesia plate boundary tectonic zone. In 2004, eight shocks of M≥7.0 occurred in this area, showing a migration from east to west. It implies that these shocks represent a correlated and consistent dynamic process along this subduction zone. These interplate events are associated with convergence of several plates and their fast motion in this region, which result in strong and complex structures and deformation. The India-Australia plate is underthrusting toward the Sunda continental block or Burma plate at a low angle, producing a great locked area on the shallow portion of the subduction zone where enormous strain is accumulated. Interseismic uplift recorded by coral growth and horizontal velocities measured by GPS show the geometry of the locked portion of the Sumatra subduction zone. The vertical and horizontal data reasonably match with a model in which the plate interface is fully locked over a significant width. This locked fault zone extends to a horizontal distance of 132km from the trench, which corresponds to a depth of 50km. The sudden ruptures and large-scale slip of this locked area as a release of stress occurred, are the direct cause of the M8.7 earthquake near Indonesia in 2004.

中国大陆的强震与火山相互作用

强震活动和火山喷发都是地球内部圈层能量交换的显著表现.新近观测研究表明:强震与火山活动存在密切的相互作用,但人类对强震与火山的孕育环境和发生过程了解还十分有限,对火山内部岩浆系统的认识还远远达不到预测强震触发火山喷发或岩浆扰动及火山流体引发强震活动的需求.中国大陆的长白山和腾冲火山区存在强震-火山相互作用的迹象,腾冲这一潜在的强震和火山活动危险区是开展强震-火山相互作用研究的理想场所.立足于中国地震科学实验场的跨学科基础观测设施和相关科研项目,有望在腾冲火山区取得强震-火山关联性研究的新突破,为有效预防强震和火山灾害及热能开发提供科技支撑.

2022年泸定M_(s) 6.8级地震发震构造与鲜水河断裂带强震迁移规律

2022年9月5日12时52分在四川甘孜州泸定县发生Ms6.8级地震,震源深度16 km。这是继2014年康定地震后,发生在鲜水河断裂带上的又一次强震。笔者等通过已有文献资料,结合鲜水河断裂带南段野外地质调查,统计了滑动速率及历史地震资料,并总结了近代鲜水河断裂带强震迁移规律,对认识鲜水河断裂带活动特征及未来地震危险性具有重要意义。主要得出以下几点认识:①鲜水河断裂带各段滑动速率差异较大,以乾宁为界,从NW至SE段整体上呈现出“先减速后加速”的滑动特点;②泸定地震发震构造磨西断裂,为一次左旋走滑事件;③川滇地区近代历史强震活跃期具有“跳跃性”迁移的特点。自1981年道孚地震后,鲜水河断裂带断进入相对平静期,持续了33 a。自2014年康定地震发生,鲜水河断裂带再次进入地震活跃期;④鲜水河断裂带的强震破裂并非单次地震的“贯通型”模式,而是多次地震的渐进式。断层间相互作用尤其是大地震的发生对断裂带强震复发间隔具有重大影响,相同断裂带的强震也会对后续地震的发生概率产生变化。

地震核心业务系统国产化迁移适配研究与实现

加快推进地震核心业务系统安全、自主、可控对国家安全意义重大。基于地震核心业务系统国产化迁移适配工作,通过对比选择,采用C86和ARM技术架构,海光和鲲鹏服务器、Kylin V10操作系统、东方通中间件、VastBase数据库作为运行环境的国产化替代方案,与X86架构下以华为应用服务器、Intel CPU、Mysql数据库、FreeBSD操作系统、Wildfly和Tomcat中间件作为运行环境的国外产品方案相比,在功能和性能上相当,可满足地震行业业务使用需求,为后期地震行业进行全面国产化替代工作提供极具价值的创新实践参考。

盐构造变形特征与变形机制:基于地震解析与构造模拟的研究探讨及对复杂构造区岩盐迁移与成矿的启示

钾盐是我国长期紧缺矿种之一,我国钾肥对外依存度约30%~45%。现代盐湖钾盐储量有限。随着多年开采,资源量锐减,亟需开展对古代深层含盐盆地的钾盐成矿研究。深入研究盐构造的变形机制与变形特征,揭示不同构造环境下盐构造变形及盐体迁移、聚集、保存规律,对我国钾盐勘探新区、新层位具有重要意义。本文综述了岩盐物理性质及盐构造驱动力,结合构造物理模拟和地震解释分析盐构造变形机制,揭示了复杂构造区岩盐迁移规律,最终以库车坳陷和勐野井地区为例,结合离散元数值模拟分析了复杂构造地区的钾盐有利成矿区。结果表明:①克拉通盆地盐构造主要受重力负载作用控制,在进积前缘产生差异负载,有利于发育大型盐刺穿构造;②拉张环境下上覆地层减薄和正断层的存在为盐底辟的上涌提供了空间,岩盐在断层处汇聚;③挤压环境下岩盐在背斜构造核部汇聚,同构造沉积、先存盐底辟、基底隆起会影响盐背斜的形成与演化;④库车坳陷岩盐在南部秋里塔格构造带和北部克拉苏构造带背斜核部汇聚增厚,北部克拉苏构造带受挤压变形强烈,南秋里塔格构造带已发现含钾显示,为钾盐有利勘探区;⑤勐野井钾盐为深部源盐、浅部聚集的“二层楼”模式,深部侏罗海相层系源盐成矿潜力巨大,地表浅层出露小范围岩盐的断裂带附近可能存在隐伏钾盐矿床。

基于PI方法的华北2019年以来3次M_(S)≥5.0地震回溯性预测研究

本文应用图像信息(PI)方法对2023年山东平原M_(S)5.5地震、2021年江苏大丰海域M_(S)5.0地震和2020年河北古冶M_(S)5.1地震进行了回溯性预测研究。以华北局部(32°N~42°N,114°E~122°E)为研究区域,在网格尺度分别为0.5°×0.5°和1.0°×1.0°且预测窗长为5 a的两组参数模型下,获取2019—2027年逐年滑动的预测窗热点演化图像。结果显示,当网格尺度为1.0°×1.0°时,PI热点效果优于0.5°×0.5°网格,且对平原地震和大丰海域地震的发震位置指示作用较好。当时间窗长和归一化阈值绝对值同时增大,个别窗口存在古冶地震的有效热点,但未找到热点能同时覆盖3个地震震中所在网格的参数模型。不同参数模型下的PI热点显示,未来3~4 a郯庐断裂带渤海段存在发生M_(S)≥5.0地震的风险。本文研究结果对于华北局部地区M_(S)≥5.0地震危险性分析具有一定的参考意义。

唐山老震区现今地震活动特征

为分析唐山老震区地震活动背景,对该区域现今地震活动特征进行研究。老震区现今地震活动与1976年唐山M S7.8地震早期余震密集区域存在一定差异,结合区域背景地震活动统计结果,认为该区域地震活动受唐山地震序列影响逐渐减弱,逐步趋近于背景地震。地震分布呈现出明显的3分区差异,主要集中于中区,东区次之,西区最弱。中等地震的空间分布特征显示,地震活动存在东、中、西区交替发震的规律。目前,唐山老震区构造应力积累加速,存在地震活动水平由平静向活跃转变的可能,需要重点关注唐山断裂带北段以及滦县—乐亭断裂和卢龙断裂的交汇区域。