Machine learning-based automatic construction of earthquake catalog for reservoir areas in multiple river basins of Guizhou province,China

Large reservoirs have the risk of reservoir induced seismicity.Accurately detecting and locating microseismic events are crucial when studying reservoir earthquakes.Automatic earthquake monitoring in reservoir areas is one of the effective measures for earthquake disaster prevention and mitigation.In this study,we first applied the automatic location workflow(named LOCFLOW)to process 14-day continuous waveform data from several reservoir areas in different river basins of Guizhou province.Compared with the manual seismic catalog,the recall rate of seismic event detection using the workflow was 83.9%.Of the detected earthquakes,88.9%had an onset time difference below 1 s,81.8%has a deviation in epicenter location within 5 km,and 77.8%had a focal depth difference of less than 5 km,indicating that the workflow has good generalization capacity in reservoir areas.We further applied the workflow to retrospectively process continuous waveform data recorded from 2020 to the first half of 2021 in reservoir areas in multiple river basins of western Guizhou province and identified five times the number of seismic events obtained through manual processing.Compared with manual processing of seismic catalog,the completeness magnitude had decreased from 1.3 to 0.8,and a b-value of 1.25 was calculated for seismicity in western Guizhou province,consistent with the b-values obtained for the reservoir area in previous studies.Our results show that seismicity levels were relatively low around large reservoirs that were impounded over 15 years ago,and there is no significant correlation between the seismicity in these areas and reservoir impoundment.Seismicity patterns were notably different around two large reservoirs that were only impounded about 12 years ago,which may be explained by differences in reservoir storage capacity,the geologic and tectonic settings,hydrogeological characteristics,and active fault the reservoir areas.Prominent seismicity persisted around two large reservoirs that have been impounded for less than 10 years.These events were clustered and had relatively shallow focal depths.The impoundment of the Jiayan Reservoir had not officially begun during this study period,but earthquake location results suggested a high seismicity level in this reservoir area.Therefore,any seismicity in this reservoir area after the official impoundment deserves special attention.

Casualties' States During Destructive Earthquakes

The index of casualties is introduced for the trapped that is still alive after a destructive earthquake to indicate his (her) injury degree. In order to describe the injury-developing process controlled by three factors: the initial injury degree, the trap surroundings and the physique of the cornered, a function SFC (State-Function of Casualties) can be naturally constructed. Through parameter analysis from eight pieces of figures, it can be found that the trapped with weaker physique and worse initial injury degree and in more adverse trap surroundings deserves sooner rescue.

Paleo and New Earthquakes and Evaluation of North Tabriz Fault Displacement in Relation to Recurrence Interval of Destructive Earthquakes

Azerbaijan is one of the most active segments of the Alpine-Himalayan seismic belt and marks the junction between the African-Arabian and Indian plate to the south and Eurasian plate to the north. Several regional earthquakes have been strongly felt and caused damages in and around Tabriz during history. For example, the magnitude 7 to 7.7 Tabriz earthquake in 1780, which is the most strongest experienced one in Lesser Caucasus and east of Turkey and caused severe damage in Azerbaijan territory including Tabriz City. The urban area of Tabriz City lies on Miocene to Quaternary soft sediments （clays, sands, silts, and gravels.） resting on an old Tertiary basement. Previous studies have shown that the thickness of such soft sediments could largely influence the site response in case of an important regional earthquake. The accurate information about historical earthquakes and new faulting is an important tool for viewing the active tectonic and analyzing the earthquake risk and seismic migration. Historical records of earthquakes in Tabriz based on macro and micro seismic observations cover period of 1,000 to 1,400 years. Our study aims at mapping the seismic response of a pilot zone of Tabriz for different earthquake scenarios, a simple but robust.

Airblast evolution initiated by Wangjiayan landslides in the M_(s)8.0 Wenchuan earthquake and its destructive capacity analysis

Airblasts,as one common phenomenon accompanied by rapid movements of landslides or rock/snow avalanches,commonly result in catastrophic damages and are attracting more and more scientific attention.To quantitatively analyze the intensity of airblast initiated by landslides,the Wangjiayan landslide,occurred in the Wenchuan earthquake,is selected here with the landslide propagation and airblast evolution being studied using FLUENT by introducing the Voellmy rheological law.The results reveal that:(1)For the Wangjiayan landslide,its whole travelling duration is only 12 s with its maximum velocity reaching 36 m/s at t=10 s;(2)corresponding to the landslide propagation,the maximum velocity,28 m/s,of the airblast initiated by the landslide also appears at t=10 s with its maximum pressure reaching594.8 Pa,which is equivalent to violent storm;(3)under the attack of airblast,the load suffered by buildings in the airblast zone increases to 1300 Pa at t=9.4 s and sharply decreased to-7000 Pa as the rapid decrease of the velocity of the sliding mass at t=10 s,which is seriously unfavorable for buildings and might be the key reason for the destructive collapse of buildings in the airblast zone of the Wangjiayan landslide.

Potential traces of earthquakes in the ancient city of Kytaia, Kerch Peninsula, Crimea

In this paper, the authors studied the traces of destruction in the fortress walls and houses of the Bosporan city of Kytaia. The study of this city has been ongoing since 1970. Over the past time, numerous damages have been identified at different sites of the ancient settlement. In the article, an attempt is made to compare some of them with the results of earthquakes on the Bosporus, about which the data of ancient authors were preserved.

Main Factors Affecting the Distribution of the Macroscopic Destruction Field of Earthquake

It is proposed that some possible macroseismic epicenters can be determined quickly from the relationship that the microseismic epicenters located by instruments bear with faults. Based on these so-called macroseismic epicenters, we can make fast seismic hazard estimation after a shock by use of the empirical distribution model of seismic intensity. In comparison with the method that uses the microseismic epicenters directly, this approach can increase the precision of fast seismic hazard estimation. Statistical analysis of 133 main earthquakes in China was made. The result shows that the deviation distance between the microseismic epicenter and macroseismic epicenter falls within the range of 35 km for 88 % earthquakes of the total and within the range of 35 to 75 km for the remaining ones. Then, we can take the area that has the microseismic epicenter as its center and is 35 km in radius as the area for emphatic analysis, and take the area within 75 km around the microseismic epicenter as the area for general analysis. The relation between the 66 earthquake cases on the N-S Seismic Belt in China and the spatial distribution characteristics of faults and the results of focal mechanism solution were analyzed in detail. We know from the analysis that the error of instrumental epicenter determination is not the only factor that gives effects to the deviation of the macroseismic epicenter. In addition to it, the fault size, fault distribution, fault activity, fault intersection types, earthquake magnitude, etc. are also main affecting factors. By sorting out, processing and analyzing these affecting factors, the principle and procedures for quickly determining the possible position of the macroseismic epicenter were set up. Taking these as a basis and establishing a nationwide database of faults that contains relevant factors, it is possible to apply this method in practical fast estimation of seismic hazard.

1875年广西与贵州之间强震与地震密集关系分析

1875年在广西与贵州之间发生了一次强烈地震,《中国历史强震目录(公元前23世纪—公元1911年)》和《中国历史地震图集》所给出的震中位置差异较大。针对相关史料进行梳理,通过计算研究区的中小地震密集区之后发现,广西乐业和贵州望谟分别存在地震密集区与上述两个震中对应。依据地震密集与历史强震的关系,分析了上述两种震中位置的合理性和可能结果,认为广西乐业和贵州望谟存在着两次6级左右的强震的可能性。

Characteristics and main controlling factors of helium resources in the main petroliferous basins of the North China Craton

At present, the main controlling factors of helium accumulation is one of the key scientific problems restricting the exploration and development of helium reservoir. In this paper, based on the calculation results of He generation rate and the geochemical characteristics of the produced gas, both the similarities and differences between natural gas and He resources in the Bohai Bay, Ordos and the surrounding Songliao Basin are compared and analyzed, discussing the main controlling factors of helium resources in the three main petroliferous basins of the North China Craton. It is found that the three basins of Bohai Bay, Ordos and Songliao have similar characteristics of source rocks, reservoirs and cap rocks, that's why their methane resource characteristics are essentially the same. The calculated ~4He generation per cubic metamorphic crystalline basement in the three basins is roughly equivalent, which is consistent with the measured He resources, and it is believed that the ~4He of radiogenic from the crust is the main factor controlling the overall He accumulation in the three basins;there is almost no contribution of the mantle-derived CH_4, which suggests that the transport and uplift of mantle-derived ~3He carried by the present-day magmatic activities along the deep-large faults is not the main reason for the mantle-derived ~3He mixing in the basins. Combined with the results of regional volcanic and geophysical studies,it is concluded that under the background of the destruction of North China Craton, magma intrusion carried a large amount of mantle-derived material and formed basic volcanic rocks in the Bohai Bay Basin and Songliao Basin, which replenished mantle-derived ~3He for the interior of the basins, and that strong seismic activities in and around the basins also promoted the upward migration of mantle source ~3He. This study suggests that the tectonic zone with dense volcanic rocks in the Cenozoic era and a high incidence of historical strong earthquakes history may be a potential area for helium resource exploration.

地震荷载作用下新三义隧道地震反应分析

为探究隧道衬砌在地震荷载作用下的破坏机理,根据新三义隧道某区段建立Abaqus数值计算模型,分析地震波施加方法对衬砌动力响应的影响,研究不同地震波类型对衬砌地震动破坏的差异,总结地震灾害对隧道衬砌的破坏机理。研究结果表明:地震波的振动输入法会导致数值模拟结果明显失真,波动输入法计算精度较高。由于结构特殊性,拱顶与侧壁避车洞会出现应力集中现象,为衬砌破坏多发处。由于隧道围岩的物理特性,岩体隧道衬砌受周围岩体的影响在一定范围内随地震动而产生整体性震动,使得隧道衬砌没有产生大范围结构性破坏。集集地震灾害对隧道衬砌造成的破坏主要由S波引起;地震对衬砌破坏过程为地震波自下而上传递到衬砌,使衬砌发生整体性震动;避车洞周围由于结构特殊性而产生超过混凝土极限强度的应力,造成衬砌发生开裂、剥落等现象。

地震烈度仪对卷积神经网络模型地震预警震级估计的影响

为探索地震烈度仪对卷积神经网络模型地震预警震级估计的影响,以2022年中国发生的5次破坏性地震(M_S≥5.8)为例,将地震数据应用到卷积神经网络震级估计模型中,分析引入烈度仪地震数据后的震级估计。结果表明:在P波到达后3 s,烈度仪和强震仪的单台震级估计误差主要分布在±1震级单位范围内;对于震中距100 km以内的数据,在P波到达后10 s内,与强震仪相比,烈度仪震级估计误差均值更接近0;对于信噪比小于20的数据,强震仪震级估计误差均值比烈度仪的震级估计误差均值更接近0,且烈度仪有更大震级估计误差的不确定度。此外,对于这5次地震,与强震仪相比,烈度仪的数量更多、分布更密,引入烈度仪地震数据后,卷积神经网络模型更快地获得鲁棒的震级估计。研究结果为地震烈度仪在卷积神经网络震级估计模型中的适用性提供了依据,也为地震预警系统震级估计提供参考。

2023年甘肃积石山M_(S)6.2地震中川乡泥流成因及破坏性分析

2023年12月18日23时59分,甘肃临夏州积石山县发生6.2级地震,并诱发了大量地质灾害,其中,中川乡砂土液化泥流灾害造成了重大的经济损失与人员伤亡,亟需对其特征、成因、破坏性进行分析厘定。根据已有文献资料,利用获取的高精度、高分辨率数字成果,借助影像解译、地面调查,对震后泥流灾害进行综合分析。结果表明:(1)易滑且饱水黄土在地震的震动载荷作用下,土体内孔隙水压力迅速升高导致砂土液化,最终土层失稳破坏,导致台地边缘垮塌与地震滑坡。土水混合物在重力作用下,顺着高差沿沟谷、冲沟前进形成液化型滑坡-泥流灾害。(2)此次灾害现象并非泥流单一作用,而是砂土液化导致的泥流和砂涌同时存在,二者同时发生的概率很低,破坏性极大。(3)此次地震为典型的“小震、中震大灾”情况,相比其他相似成因液化滑坡灾害,其规模更大;相比其他相近震级地震,其造成的破坏及伤亡更大。此次地震诱发的地质灾害具有一定的特殊性与异常性。

四维灾体模型在新疆地震灾害中的应用与分析

在四维灾体模型基础上,结合地震灾害相关因素,对该模型进行了应用与初步分析。通过计算2002—2022年新疆地区遭受具有破坏性地震的灾体量指数,进一步进行灾度分级。为了验证模型的准确性,将计算结果与已有三维灾体模型的结果进行对比,并分别计算汶川和唐山及其他地震的灾害损失。研究结果表明,在考虑更为丰富的灾情信息前提下,本模型的计算结果较为准确且符合灾害损失的实际情况。

四川省汶川地震灾区干线公路典型震害特征分析

基于地震灾区的大量调查、检测、评估与抢通保通的成果,概括介绍了汶川大地震后四川省公路总体损毁情况;归纳总结了四川省国省干线公路工程路基、路面、桥梁、隧道等结构物典型震害特征,并从地质和工程角度简要的分析了震害产生原因。桥梁毁坏程度与发震断裂的距离有很大的关系,隧道破坏程度不仅与发震断裂距离有关,而且与组成围岩的岩性有关,断裂带附近软硬相间的沉积岩隧道震害较为严重,花岗岩隧道震害轻微。边坡震害与断层带距离和组成边坡的岩性、坡度等有关,断裂带附近花岗岩、石灰岩及砂岩等组成的高陡边坡崩塌、滑坡等次生地质灾害非常严重。

云南地震灾害人员伤亡预测方法研究

以1992～2010年云南地区的破坏性地震的伤亡人数资料为主,将其分别与地震震级和烈度统计拟合,得到云南地区震级和烈度与死亡人数的关系曲线及表达式。根据云南各地的自然环境和社会发展的差异,确定了各种条件下的地震灾害人员死亡影响因子加权系数的取值,对两个拟合关系表达式进行校正。采用该方法计算了已发生的12个地震的死亡人数,并与实际的地震灾害死亡人数作了对比及讨论。

破坏性地震的应急通信需求与应用初探

通过分析MS5～6、MS7～8及MS8以上地震案例造成的地面通信受损规律,剖析不同震级地震应急通信的主体通讯业务,针对目前地震行业的通信技术系统现状,探讨了地震应急通信开展方式。

芦山地震中大跨空间结构主要破坏模式及数值分析

2013年4月20日在四川省雅安市芦山县发生了7.0级地震,地震造成196人死亡和21人失踪,经济损失亦极其巨大。此次地震中一些大跨空间钢结构发生较显著的破坏,这是与以往历次震害最大的不同之处。文中总结了芦山体育馆和芦山中学体育馆这两个大跨空间钢结构在此次地震作用下结构发生破坏的主要部位和典型的破坏模式,并分析造成这些破坏的主要原因。针对芦山县体育馆进行现场实测,并与震害结果进行对比,结果表明,结构发生了较明显的扭转现象。以芦山县中学体育馆为例,通过有限元软件ANSYS对其地震下的破坏机理进行数值模拟,并与实际震害进行对比分析。在此基础上,对大跨空间钢结构的抗震设计和施工提出一些合理的意见和建议。

地震次生毒气泄漏与扩散的数值模拟与动态仿真

文章对破坏性地震中可能发生的次生毒气泄漏与扩散灾害进行了数值模拟与动态仿真研究 ,设定了几种有实际意义的数值分析模型 ,分别进行了结构地震破坏、有毒有害气体泄漏、在一定泄漏和气象条件下的向周围空间扩散的动态仿真研究 ,给出了典型毒气扩散过程中可致人员死亡、严重危险和有感区域的范围的动态变化结果。作者认为地震次生毒气泄漏与扩散研究对大地震应急、城市和大型企业防灾都有重要的意义和广阔的应用前景。

永胜6.0级地震的破坏特征及分析

介绍了永胜 6 0级地震震区的自然概况、震害分布及特征 ,分析了各种破坏产生的机理 ,提出了震区在恢复重建与规划发展时的建议以及各类建 (构 )筑物加强抗震的措施。

城市破坏性地震应急预案的编制与修订要点探讨

破坏性地震应急预案是城市防震减灾工作的核心内容之一,是破坏性地震发生后进行应急处置的指导性文件。根据综合分析国外部分地区的防灾规划中地震应急处置的内容与特点,研究了目前我国部分城市的破坏性地震应急预案现状和存在问题。并在此基础上,探讨了城市破坏性地震应急预案中防御水准的制定、灾害信息的收集和传递、辅助决策保障、应急救灾反应以及对人文和环境的考虑等关键问题及其解决方法,为城市破坏性地震应急预案的编制或修订提供参考。

2003年大姚6.2级地震房屋震害特征及分析

介绍了 2 0 0 3年 7月 2 1日大姚 6 2级地震震区的房屋概况 ,分析了地震的破坏作用和各种结构房屋的震害特征 ,提出了震区恢复重建与规划发展的建议及各种结构房屋加强抗震的措施。