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1.
Although Tanlu fault is one of the most important tectonic fault zones and active earthquake belts in eastern China, little is known about its deep structure. In this study, we use the existing Bouguer gravity data to study the middle section of the Tanlu fault zone, which is also known as the Yishu fault zone. Our gravity inversion results indicate that the Moho has an abrupt offset in depth at the Tanlu fault zone and it has a relatively smooth variation away from the fault zone. The crustal structures on both sides are different from each other. Sediment is thin on the west side with an average thickness of less than 5 km, while it is as thick as 6 km on the east side. The thinnest sediment （3-4 km） is at the fault zone. Moho depth increases from 33 to 34 km on east side and from 36 to 38 km on west side. Tanlu fault zone is shown as a wide zone of linear gradient in the Bouguer gravity anomaly. 相似文献
2.
Controlling factors for gas hydrate occurrence in Shenhu area on the northern slope of the South China Sea 总被引：1，自引：0，他引：1
WANG HongBin YANG ShengXiong WU NengYou ZHANG GuangXue LIANG JinQiang CHEN DuoFu 《中国科学:地球科学(英文版)》2013,(4):513-520
Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred in limited areas of the slope. Drillings in the BSR-distributed area (the District S) on the northern slope of the South China Sea suggested that gas hydrate only occurred at Sites SH2, SH3, and SH7 with high saturation (up to 20%-40%), and there is no hydrate at Sites SH1 and SH5 although the distance between SH1 to SH3 is only 500m. In this paper, we investigated seafloor gradient, fault development, temperature, and pressure in the District S on the northern slope of the South China Sea to understand the possible factors con- trolling BSR distribution and gas hydrate occurrence. The District S is a structurally fractured continental slope zone and its seafloor gradient varied greatly. The BSR-occurred areas have an average gradient of 19.89×10 2 whereas the BSR-free zone has the average gradient of 10.57×10 2 . The calculated relative structural intensities from fault densities and displacements show that the BSR-distributed areas tend to occur in the areas with a moderately high structural intensity, where faults frequently developed close to the seafloor that are possibly favored for lateral migration of gases. On the basis of temperatures and pressures at drilling sites, hydrate-occurred Sites SH2, SH3, and SH7 are located within the thermodynamically stable area for methane hydrate, and hydrate-absent Sites SH1 and SH5 are out of the thermodynamically stable area for methane hydrate formation, suggesting that both BSR and the thermodynamic stability are necessary for hydrate occurrence in the subsurface. 相似文献
3.
Based on the convection and diffusion mechanisms of radon migration, in this paper we deduce the two-dimensional differential equation for radon transportation in the overburden above active fault zones with an unlimited extension along the strike. Making use of the finite difference method, the radon concentration distribution in the overburden above active faults is calculated and modeled. The active fault zone parameters, such as the depth and the width of the fault zone, and the value of radon concentration, can be inverted from the measured radon concentration curve. These realize quantitative interpretation for radon concentration anomalies. The inversion results are in good agreement with the actual fault zone parameters. 相似文献
4.
《中国地震研究》1997,(3)
In this paper,measurements of gaseous radon and gaseous mercury densities were conducted for the first time along the Haiyuan active fault zone,including three longer secondary shear faults from Biangou to Shaokou,faults in the Ganyanchi pull-apart basin,and the Biangou push-up structure as well as the thrust fault at the eastern pediment of Liupanshan Mountain in the terminal compressional area.Then relations between fracture gas densities and faulting activity were analyzed.The results show that there is a distinct corresponding relation between gaseous radon and gaseous mercury densities and faulting activity,when the measurement conditions are basically the same,and it proves that the fault gasmetry method is an effective technique for study the activity and segmentation of active faults. 相似文献
5.
The Xiannvshan fault zone, lying along the western margin of the Huangling anticline, is one of the most important fault zones in the Three Gorges reservoir area. The fault experienced strong activity during the Cenozoic Era. The question of whether the fault zone goes through the Yangtze River has been one of the key problems faced in previous studies as it has a significant influence upon the assessment of geological hazards and earthquake stability in the reservoir area. Based on tectonic and geomorphic observations along the fault zone between the Baixianchi village in Changyang county and Huangkou village in Zigui town, together with the comparisons between the geology in Guizhou and Quyuan town in the north bank of the Yangtze River and the Xiannvshan fault zone, it is suggested that the north end of this fault zone is located around Huangkou village and does not go through the Yangtze rivers northward. The evidence is as follows: ① On the basis of field data collection, it is found that the Xiannvshan Fault zone, which stretches 80km, underwent thrust movement in the Cenozoic period, resulting in ravines and fault scarps, topographically. Whereas, on the northern bank of the Yangtze River, faults are rarely found, and most of the faults are developed in the Jurassic strata,without topographical effects. Therefore, the Xiannvshan Fault zone has not stretched to the north bank of the Yangtze River. ② The fault gouge and tectonite zone were found developed on the Xiannvshan Fault zone at Baixianchi village, but only a tectonite zone was found at Zhouping village. There are also some branch faults close to the northern end of the fault zone. So, the activity of the fault zone weakened from south to north in Cenozoic. The fault zone extends northward and dies out at Huangkou. It doesn’t stretch forward any longer as indicated by continuous strata, sparse joints, and small folds, etc. 相似文献
6.
Effect of thermal stimulation on gas production from hydrate deposits in Shenhu area of the South China Sea 总被引：1，自引：0，他引：1
The Shenhu area on the northern continental slope of the South China Sea (SCS) is one of the promising fields for gas hydrate exploitation. The hydrate-bearing layer at drilling site SH2 is overlain and underlain by permeable zones of mobile water. In this study a vertical well was configured with a perforated Interval I for producing gas and a coiled Interval II for heating sediment. The hydrate is dissociated by a small depressurization at Interval I and a thermal stimulation at Interval II. The numerical simulations indicate that the thermal stimulation has a significant effect on gas release from the hydrates in the production duration and improves the gas production in the late period. The gas released by thermal stimulation cannot be produced as quickly as the production gets operated because of the hard pathway for fluids to flow in the sediments. The gas production is enhanced due to the heating for 7242 m 3 in the whole production. Increasing heating temperature at Interval II can improve gas production and restrain water output, and advance the arrival time of the gas flow from the zone at Interval II. The absolute criterion and relative criterion suggest that the thermal stimulation in the production schemes is pronounced for releasing gas from the hydrate deposit, but the production efficiency of gas is limited by the sediment of low permeability. The study provides an insight into the production potential of the hydrate accumulations by thermal stimulation with depressurization in two wells, and a basis for analyzing economic feasibility of gas production from the area. 相似文献
7.
Chen Daqing 《中国地震研究》2007,21(3):333-344
The observation of water temperature in deep wells has been carried out for more than 20 years in China.However,study on the mechanism of water temperature response to earthquakes is inadequate.During the study of the co-seismic response characteristics of water level and temperature in 121 wells within the China subsurface fluid monitoring network at the time of the December 26,2004,M-S8.7 Indonesia earthquake,we found regular response characteristics,that is,when the water level in a deep well oscillates,the water temperature in the same well will mostly experience a cycle from dropping to restoration at the same time.The process will continue for dozens of minutes to several hours.In order to confirm the observed phenomenon,we collected the digital water level and temperature observation data for 39 far-field strong earthquakes from the Tangshan well in Hebei Province(with the data set beginning in 2001).The same response characteristics were observed.Based on the analysis of the influencing factors that may cause the water temperature drop,the authors suggest the gas escape mechanism for co-seismic water temperature drop and posit two main factors that influence the water temperature drop during the process of gas escape.Finally,the authors provide a rational explanation of some observed phenomena based on the mechanism. 相似文献
8.
LING WenLi XIE XianJun LIU XiaoMing & CHENG JianPing Faculty of Earth Sciences China University of Geosciences Wuhan China State Key Laboratory of Geological Processes Mineral Resources China University of Geosciences Wuhan China Key Laboratory of Continental Dynamics Northwest University Xi’an China 《中国科学D辑(英文版)》2007,50(6):813-824
A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the method of in situ ablation of a 193 nm excimer laser system coupled with an up to date ICP-MS system. Among the three formations of the Qingshan Group, zircons recovered from the lowest part of the Houkuang Fm. were dated at 106±2 Ma (95% confidence, the same below), whereas those from the lower and upper parts of the Shiqianzhuang Fm. were given ages of 105±4 Ma and 98±1 Ma, respectively. A spatially decreasing trend for the Mesozoic magmatic timing from west to east in the province is observed through comparing the data of this study with those by previous works on the Qingshan volcanic lavas occurring at western Shandong and within the Yishu fault zone. The Qingshan volcanic rocks are constituent of the 'Shoshonite Province' in East China. Exposed at most provinces of central East China along the Tan-Lu fault and the Yangtze fault zones, these volcanic suites are characterized by shoshonite and high-K calcalkalic rocks in lithology and thought to be correlated with the partial melting of continental mantle in genesis. It is also shown that the Qingshan potassic volcanic suite from eastern Shandong basins is distinctly younger than those from other ar-eas of the shoshonite province. By contrary, ages of the Mesozoic to Cenozoic alkaline basalts, sourced by asthenospheric mantle, from both northern Huaiyan basin and northern Dabie belt along the Tan-Lu fault zone and from the Ningwu, Lishui and Luzong basins along the Yangtze fault zone are observably older than those occurring within eastern Shandong. The revealed temporal and spatial patterns in magmatism for the two types of volcanic suites make an important geochronological con-straint on the Mesozoic to Cenozoic dynamic evolution model of the subcontinental lithosphere in East China. 相似文献
9.
In order to image the 3-D velocity structure of its shallow crust in Kunming region,China,finite-difference seis-mic tomography is used to invert the seismic data selected carefully from six-shot data. The result lays a founda-tion for the discussion of the relationship between the obtained velocity structure and the hidden faults,and for the illumination of the depth extents of main active faults surrounding Kunming city. Puduhe-Xishan fault lies on the western margin of the Kunming basin and is just situated on the west edge of the low velocity anomaly zone found at all depth levels. This indicates that this fault is a borderline fault of the Kunming basin. It can be concluded that the fault dips eastwards with a steep angle and its depth extent is large. Puji-Hanjiacun fault and Heilong-tan-Guandu fault play a role in controlling the low velocity anomaly zone in middle basin. The depth extents of the two faults are comparatively small,without traversing the interface of basin floor. 相似文献
10.
Seismotectonic Environment for Zhangbei-Shangyi Earthquake and Characteristics of Macroscopic Damage
Xu Xiwei Rang Yongkang Zhou Bengang Yin Gongming Li Jianhua and Liu WuzhouInstitute of Geology CSB Beijing China 《中国地震研究》1999,(3)
The regional seismotectonic environment for the Zhangbei- Shangyi earthquake is described, and in combination with the distribution of macroscopic seismic intensity, source mechanism solution, and interpretation of lineaments on satellite images, the seismogenic structure for the earthquake and possible seismogenic fault are discussed in this paper. It is suggested that the Zhangbei-Shangyi earthquake is a result of the latest movement along the northwestern termination of the Zhangjiakou-Penglai fault zone and we should pay serious attention to the future trend of seismic activity along this fault zone. 相似文献
11.
根据前人对西秦岭北缘断裂带上历史地震及古地震复发周期和离逝时间等的综合研究,得出该断裂存在发生强震的较大潜在风险,因此加强对该断裂现今构造活动的定点监测和地震预测预报具有重要现实意义。据此,根据断裂逸出气体测项剖面浓度分布（变化）特征,在西秦岭北缘断裂带（天水段）上新建3个断层土壤气连续观测站,开展断层气（H2、CO2、Rn、CH4）浓度观测,分析断裂带不同段深部气体特征的空间差异及其随时间的变化特征,监测甘东南地区应力调整与地震活动。初步观测资料分析表明：在正常情况下其背景值比较稳定,且同一测项在不同测点变化形态具有相似性、同步性,说明观测资料真实可靠,并具有可比性。各测点出现测项同步异常变化时,可能反映了区域应力调整及变化状态,对震情跟踪和地震预测提供参考判据。 相似文献
12.
采用网格化布点野外流动观测的方法测量了汤阴地堑南部380个点的土壤 H2 浓度,分析其空间分布特征及其与构造的关系,并进一步揭示出气体地球化学特征与区域地质构造背景间的联系. 研究结果表明,汤阴地堑南部土壤 H2 浓度介于(0．26~175．50)×10-6,背景均值为(17．25±11．19)×10-6,异常阈值下限为57．30×10-6.在空间上,土壤 H2 呈现出西低东高的分布特征,受覆盖层厚度和地表沉积特征的影响,低于背景值的测点主要分布于研究区西部.高值异常测点主要集中在研究区东部并沿汤中、汤东断裂带分布,H2 浓度等值线高值中心点连线与断裂带走向基本一致,汤西断裂带虽没出现高值异常,但 H2 浓度相对高值仍然在断裂带及邻近区域,反映出构造对 H2 释放的控制作用.同时,土壤 H2 等值线空间分布也显示,在研究区存在一条北东-南西向的 H2 浓度高值异常条带,推测存在一条规模较大的隐伏断裂.研究区主要断裂带 H2 浓度表现为汤西断裂带显著低于汤中、汤东断裂带,而异常衬度表现为汤西断裂带、汤中断裂带小于汤东断裂带.结合研究区地球物理探测资料分析认为 H2 浓度及异常衬度是构造活动背景的反映,部分深部来源的 H2 通过深大断裂及有利的深浅构造组合向地表扩散迁移,在地壳浅部与浅源 H2 混合,并在断裂带上覆土壤层形成浓度高值异常条带.需进一步开展 H2 在汤阴地堑南部构造活动监测中的应用探索.同时也需要对研究区由北东-南西向 H2 浓度异常条带而推测出的隐伏断裂开展进一步深入研究. 相似文献
13.
采用ATG-6118H痕量氢在线自动分析仪，在朱夏-商丹断裂带南阳地区布设独山、马山口2个氢气观测台，研究设备取气深度、抽气时间设置长短对观测断层氢气浓度的影响，从而为利用痕量氢设备进行断层氢气观测提供参考依据。实验结果表明：①取气深度越浅，观测到的氢气浓度越高，日变化幅度越大；②集气管内氢气浓度偏低时，抽气时间设置略高于导气管路排空时间，氢气浓度明显变化，否则变化不明显。 相似文献
14.
为探究卫辉西代村跨断层短水准出现的趋势性变化与断裂活动间的相关性，在跨断层水准观测场地布设1条土壤气Rn和H2浓度测线，复测周期与跨断层水准测量周期基本一致，分别于2018年4月、7月、10月开展3期土壤气Rn和H2浓度测量。同时，为增加观测数据的可靠性，于2018年8月布设了1条与上述3期测线平行的测线并开展土壤气Rn和H2浓度测量。4期土壤气H2浓度测量结果显示，该区土壤气H2浓度背景值处于较低水平，H2浓度异常值所处位置主要集中在距起点150—210 m处，该处为断裂通过处。4期中Rn浓度最大值、背景值和均值的变化幅度均在正常范围内，Rn浓度异常值所处位置也主要集中在距起点150—210 m处，该处可能为断裂通过处。土壤气显示的断裂通过处与该区探槽显示的断裂位置一致。4期土壤气测量结果表明，近期汤西断裂带可能处于相对稳定状态，跨断层水准观测数据的趋势性变化与断裂活动之间相关性不大。 相似文献
15.
为探究卫辉西代村跨断层短水准出现的趋势性变化与断裂活动间的相关性,在跨断层水准观测场地布设1条土壤气Rn和H2浓度测线,复测周期与跨断层水准测量周期基本一致,分别于2018年4月、7月、10月开展3期土壤气Rn和H2浓度测量.同时,为增加观测数据的可靠性,于2018年8月布设了1条与上述3期测线平行的测线并开展土壤气Rn和H2浓度测量.4期土壤气H2浓度测量结果显示,该区土壤气H2浓度背景值处于较低水平,H2浓度异常值所处位置主要集中在距起点150—210 m处,该处为断裂通过处.4期中Rn浓度最大值、背景值和均值的变化幅度均在正常范围内,Rn浓度异常值所处位置也主要集中在距起点150—210 m处,该处可能为断裂通过处.土壤气显示的断裂通过处与该区探槽显示的断裂位置一致.4期土壤气测量结果表明,近期汤西断裂带可能处于相对稳定状态,跨断层水准观测数据的趋势性变化与断裂活动之间相关性不大. 相似文献
16.
川滇地震预报实验场高精度氢观测台阵建设分析 总被引：2，自引：0，他引：2
氢气动态与断裂活动、 地震的关系密切。 在川滇实验场范围内的安宁河断裂带和则木河断裂带选取典型场地, 建设由连续观测点和定期观测点组成的观测台阵, 开展连续高精度氢浓度、 同深度地温和环境气温、 气压同步观测, 进行氢气观测技术研究工作。 着重介绍高精度氢地震观测台阵的设计思路、 建设内容以及运行情况, 并分析了观测数据。 结果表明, 观测台阵建设的技术指标达到设计目标, 并讨论出了断裂带土壤氢气连续观测与定期观测点的建设方案与技术指标。 为期一年的连续观测数据显示, 氢气浓度背景呈现出“北高南低”的分布格局, 暗示了不同构造区氢气浓度的背景特征。 相似文献
17.
基于祁连山断裂带中东段9个观测点2016—2021年的土壤气体氡浓度观测数据，深入分析其浓度强度时空分布特征。同时结合历史大震背景、现今地震活动与断裂带滑动速率的对比分析，从地球化学的角度对祁连山断裂带中东段进行地震危险区段判定。研究表明：祁连山断裂中东段土壤气体氡浓度强度的空间分布特征为东强西弱，其时间序列变化特征总体呈下降趋势；断层土壤气氡浓度强度的空间分布特征、历史及现今地震活动和断裂滑动速率具有较好的耦合性。研究结论可以提供研究区深部地下流体活动的证据，对进一步研究追踪未来可能发生地震的断层和活动段具有重要意义。 相似文献
18.
19.
2017—2018年在依兰—伊通断裂黑龙江段开展断层氢气调查工作，沿断裂选取8个剖面进行跨目标断层观测及土壤氢气采样。结果表明：①断层氢气浓度常存在异常变化；②不同类型的断层，氢气浓度异常变化幅度没有明显差异；③走滑断层异常特征一般为断层两侧低、中间高，呈现“低—高—低”的特点；倾滑断层异常特征一般为断层的上盘略高、下盘略低；④断层氢气排放不仅受微观局部断层的影响，更受宏观的地震活动性大环境的影响。 相似文献
20.
有研究认为1989年和1991年阳原盆地西侧冀晋交界附近发生的2次中强地震震群导致盆地东侧应力随之调整,意味着阳原盆地开启了新的地震活跃周期。盆地东侧地震活动主要集中在盆地北缘断裂附近,其中段大蟒沟至台家庄为该北缘断裂最活动段,该断裂带的最新活动情况对于震情形势分析具有重要意义。本研究在河北阳原盆地北缘断裂带中段的大蟒沟、姚家庄、南口村、台家庄布设了4条测线开展2期Rn、CO2及Hg浓度测量,在南口村、台家庄剖面开展一期土壤化学成分分析,以研究该盆地北缘断裂带中段土壤气体地球化学特征空间差异及其与断裂活动的关系。结果表明:气体浓度高值点分布在断层陡坎、破碎带上,利用断层气在该区域探测隐伏断裂的浅层位置具有可行性;南口村剖面土壤气体释放强度相对高于其他剖面,这种浓度空间分布差异性可能是由于地质构造结构与断裂活动性引起的断裂破碎程度不同所致;土壤中总汞(THg)含量与气体浓度空间分布上具有一定吻合性,基于土壤中总有机碳(TOC)能够吸附Hg元素的特征,THg浓度分布特征能反映一段时间内断层活动状态;结合断裂带周边定点前兆连续观测数据及地震活动性分析认为,该断裂目前活动水平相对较弱。 相似文献