共查询到20条相似文献，搜索用时 562 毫秒
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跨断层形变测量在寻找地震前兆信息和强震预测预报工作中做出了重要贡献。2022年青海门源M6.9地震前,祁连山—海原断裂带上的跨断层短水准资料有着显著的前兆异常。本文基于截至2021年12月的跨断层短水准资料,利用时序分析法、形变异常强度分析法和垂直形变累积率分析法等,提取震前异常的时空演化特征,探讨震前中短期断层活动情况及其变形机理。结果表明,在NE—SW向挤压和NW—SE向水平剪切共同作用的动力学背景下,震源区垂直形变趋势累积处于高值,具有一定的应变能累积背景;在震前5年时间,靠近震中的断层运动发生偏离线性的“迟滞”现象,且在震前2年内异常空间分布具有向震中迁移集中的特征,表征靠近震源区地壳应力快速积累,应力局部化增强;震前半年内,距离震中60～120 km范围多个场地表现为一致性的、与挤压受力背景相反的张性异常变化,这种异常现象指示近震区应力积累到一定程度后发生微动态调整、断层局部出现预滑动等变化。 相似文献
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利用1999~2015年流动GNSS观测资料及处理结果,分析了九寨沟M_S7.0地震前区域水平形变场及其变化,得到以下认识:(1)九寨沟M_S7.0地震震源区在汶川8.0级地震之前为右旋剪切形变,汶川地震之后为左旋剪切形变;(2)2011年以来震源区左旋剪切形变持续较弱,较大的左旋剪切形变位于其西南;(3)震源区最大剪切应变、最大主应变、最小主应变均较弱;(4)九寨沟地震的发生与汶川地震的发生与否有一定的关系方面,龙门山断裂带的活动处在闭锁时段时则有所抑制或推迟九寨沟地震的发生,汶川地震后龙门山断裂带一定程度的解锁则有助于九寨沟地震的发生或促使发震时刻有所提前;(5)距震中近70km的SCSP站出现了7.1mm的南向同震位移,其他连续站未发现同震位移。 相似文献
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断层活动协调比方法在分析云南地区的地壳应变积累上具有适用性。利用区域11处跨断层流动监测场地的三十余年观测资料,首先计算跨断层场地的三维活动量,进而得出场地的断层活动协调比参数,结果显示:(1)丽江、永胜、剑川、石屏、建水场地在对应6~7级地震上,历史映震效果良好;云南地区近期存在异常的跨断层监测场地有剑川、石屏和建水场地,存在应变积累、断层活动出现异常的断裂有剑川断裂和石屏-建水断裂;(2)结合跨断层原始观测数据和三维活动量时序曲线,综合认为云南地区地壳形变异常区域分布在滇西北地区的剑川、下关和永胜以及滇中地区的峨山、石屏和建水附近;(3)结合地震活动性资料,综合认为四川九寨沟7.0级地震后,南北地震带南段应力可能会加速积累,应重点关注云南地区的中强震危险性。 相似文献
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芦山MS7.0级地震前的形变空区特征研究 总被引：3，自引：2，他引：1
上世纪70年代以来,国内外基本形成了以监测震中附近断层预滑动进行地震预测的研究思路,但近些年来,一些大地震前近震源区域的形变变化却引起了巨大的争议.本文应用芦山地震震中附近跨断层及连续形变观测资料,分析了震前不同阶段地形变变化的特点,讨论了震中附近区域异常时空演化过程.分析结果表明,沿鲜水河断裂带一些跨断层基线、安宁河及则木河断裂带个别场地的跨断层水准基线出现的显著异常变化,这些异常出现在远离芦山地震震中的区域上;在近震源区域,在龙门山断裂带南段的一些断层水准变化量极小,在鲜水河、龙门山和安宁河3条主要断裂围成的三叉口地区,倾斜、应变、重力及断层水准和蠕变观测临震前未有显著的异常变化,该区是形变变化或形变异常分布的“空区”.本文也与汶川地震前形变异常分布进行了对比,认为震前形变“空区”现象可能是强震前的一种共性特征. 相似文献
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《国际地震动态》2021,(8)
针对2008年汶川M_S8.0地震、2013年雅安芦山M_S7.0地震和2017年九寨沟M_S7.0地震前后出现的热红外现象,对MODIS卫星1 km高分辨率亮度温度的原始数据进行均线差值振幅波动水平分析发现:(1)这3次地震前在震中附近区域均出现显著的差值振幅变化异常,先为低值异常,低至历史平均水平的50%以下,后又演变为高值异常,高值异常峰值均大于历史平均水平3倍以上;(2)汶川地震、雅安芦山地震、九寨沟地震分别在高值异常峰值的55天、35天、22天后发生;(3)异常优势分布区域并不在震中区域:汶川地震震前异常区主要位于震中西北区域的柴达木块体,雅安芦山地震、九寨沟地震震前异常区域位于震中西部的巴颜喀拉块体,其中,汶川地震震前异常区域面积远远大于后者。 相似文献
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<正>1997年至今围绕巴颜喀拉块体发生了一系列强震,为块体边界跨断层形变过程与强震活动研究提供了一个前所未有的范例。鲜水河、龙门山断裂带分别属于巴颜喀拉块体的西南边界和东边界,跨断层形变观测有几十年的记录。本文基于这些数据,结合GPS观测、震源机制解、地震活动性资料,着重关注这2条断裂带跨断层形变的时空演化过程和巴颜喀拉块体的强震活动,以及它们共同反映的巴颜喀拉块体的运动。跨断层形变随时间的演变和在空间上的差异,是断层活动在时、空两个维度中的表现, 相似文献
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以合肥地震台跨断层短水准数据,结合地区小震释放能量,分析历史测量资料在地震期间的变化,并研究辅助资料对测量资料的影响,得出:①降水可能造成敏感地块的断层形变异常,但在区域应力作用断层到一定强度时,断层形变异常仍具有一定前兆意义;②安徽地区小震释放能量与合肥地震台断层形变存在一定相关性,断层活动连续几个月持续拉张或挤压,... 相似文献
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九寨沟地震(M_s7.0或M_w6.5)震中位于青藏高原巴颜喀拉块体东缘东昆仑断裂带东端塔藏断裂、岷江断裂和虎牙断裂交汇部位,中国地震局相关科研机构的研究人员曾将该震中区判定为玛沁—玛曲高震级地震危险区.地震应急科学考察期间没有发现地震地表破裂带,但地震烈度等震线长轴方位、极震区基岩崩塌和滑坡集中带、重新定位余震空间展布和震源机制解等显示出发震断层为NNW向虎牙断裂北段,左旋走滑性质,属东昆仑断裂带东端分支断层之一.此外,汶川地震后,在青藏高原东缘和东南缘次级活动断层上发生了包括2017年九寨沟地震(Mw6.5)、2014年鲁甸(M_w6.2)、景谷(M_w6.2)、康定(M_w6.0)等多次中强地震,显示出青藏高原东缘至东南缘各块体主干边界活动断层现今处于中等偏高的应变积累状态,即在巴颜喀拉、川滇等块体主干边界活动断层上具备了发生高震级(M_w≥7.0)地震的构造应力-应变条件,未来发生高震级地震的危险性不容忽视. 相似文献
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In this paper, we give a brief introduction to the proposal and development history of the earthquake magnitude concept. Moment magnitude MW is the best physical quantity for measuring earthquakes. Compared with other magnitude scales used traditionally, moment magnitude is not saturated for all earthquakes, regardless of big and small earthquakes, deep and shallow earthquakes, far field and near field seismic data, geodetic and geological data, moment magnitude can be measured, and can be connected with well-known magnitude scales such as surface wave magnitude MS. Moment magnitude is a uniform magnitude scale, which is suitable for statistics with wide magnitude range. Moment magnitude is the preferred magnitude selected by the International Seismological community, and it is preferred by the departments responsible for publishing seismic information to the public.Moment magnitude is a uniform magnitude scale, which is suitable for statistics with wide magnitude range. Moment magnitude is a preferred magnitude for international seismology, it is preferred by the agency responsible for providing information about earthquakes to the public. We provide all formulas used in the calculation of moment magnitude, and the calculation steps in detail. We also analyzed some problems and rules to solve these problems by using different formulas and numerical value calculation steps. 相似文献
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The New Magnitude National Standard of General Rules for Earthquake Magnitude( GB17740-2017) is the state mandatory standard. It was released on May 12,2017,by the General Administration of Quality Supervision,Inspection and Quarantine of the Peoples Republic of China and the Standardization Administration of the Peoples Republic of China. This paper introduces the necessity of revising the national standard of magnitude,and the main contents,technical points and primary features of the new national standard of magnitude,so that it can be applied better in practice. 相似文献
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The compression wavefield is efficiently converted to shear-wave energy at post-critical angles in areas of high impedance contrast at the sea floor. We have analysed mode-converted shear waves in a data set acquired with a hybrid marine/land geometry in Isfjorden, Svalbard. Through a kinematic 2D ray-tracing modellingV
p/Vs ratios for part of the uppermost 5km of the crust are obtained. Low values (V
p
/V
s
=1.65) are tentatively associated with the section of Devonian sandstones which appears to attain a minimum thickness of 1.5km below 3 km depth about 10km west of Kapp Thorden. 相似文献
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以青海、新疆、西藏地区为研究区域,系统研究总结了该区域2010—2020年5.0级以上地震前Wq值的时空演化特征,并以2020年新疆于田6.4级和西藏尼玛6.6级地震为实例进行阐述。得出以下三点认识:①地震一般发生在Wq值异常扩展时段或扩展—减小时段,6.0级以上Wq值异常的震例中,约81%发生于异常出现后的9个月内;②地震一般位于Wq值异常面积扩展区或扩展—减小恢复区附近,近70%的震例发生在Wq值异常区内;③建立了震级与Wq值异常区面积间的正相关统计模型,二者的相关系数(R)为0.85,为预测青海、新疆和西藏地区地震的强度提供了定量关系。青海、新疆和西藏地区Wq值方法对6.0～6.9级地震的预测效果(Wq值异常的地震报准率为61%)优于5.0～5.9级地震(Wq值异常的地震报准率为26%),为我国地球物理观测程度较低地区开展强震中短期(1年内)预测提供了参考依据。 相似文献
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A tomographic study of the V
p and V
p/V
s structures in the crust and upper mantle beneath the Taiwan region of China is conducted by simultaneous inversion of P and
S arrival times. Compared with the previous tomographic results, the spherical finite difference technique is suitable for
the strong heterogeneous velocity structure, and may improve the accuracy in the travel time and three-dimensional ray tracing
calculations. The V
p and V
p/V
s structures derived from joint inversion and the relocated earthquakes can provide better constraints for analyzing the lateral
heterogeneity and deep tectonic characters in the crust and upper mantle. Our tomographic results reveal significant relations
between the seismic wavespeed structure and the tectonic characters. In the shallow depth, sedimentary basins and orogen show
distinct wavespeed anomalies, with low V
p, high V
p/V
s in basins and high V
p, low V
p/V
s in orogen. As the suture zone of Eurasian Plate and Philippine Sea Plate, Longitudinal Valley is characterized by a significant
high V
p/V
s anomaly extending to the middle-lower crust and upper mantle, which reflects the impact of rock cracking, partial melting,
and the presence of fluids. In the northeast Taiwan, the V
p, V
p/V
s anomalies and relocated earthquakes depict the subducting Philippine Sea Plate under the Eurasian Plate. The high V
p of oceanic plate and the low V
p, high V
p/V
s atop the subducted oceanic plate extend to 80 km depth. Along the east-west profiles, the thickness of crust reaches 60 km
at the east of Central Range with eastward dipping trend, which reveals the eastward subduction of the thickened and deformed
crust of the Eurasian continental plate.
Supported by Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX3-SW-234-2), National Basic Research
Program of China (Grant No. 2007CB411701), National High Technology Research and Development Program of China (Grant No. 2006AA09A101-0201)
and National Natural Science Foundation of China (Grant Nos. 40804016, 40704013) 相似文献
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Bian Yin-ju 《地震学报(英文版)》2005,18(4):441-450
We try to give a quantitative and global discrimination function by studying m
b/M
S data using Fisher method that is a kind of pattern recognition methods. The reliability of the function is also analyzed.
The results show that this criterion works well and has a global feature, which can be used as first-level filtering criterions
in event identification. The quantitative and linear discrimination function makes it possible to identify events automatically
and achieve the goal to react the events quickly and effectively.
Contribution No.05FE3018, Institute of Geophysics, China Earthquake Administrtion. 相似文献
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内蒙古地震台网近震震级与面波震级间转换关系研究 总被引：2，自引：0，他引：2
利用内蒙古及周边2008~2015年11月116次M_L≥3.8地震资料,重新测定近震震级M_L、面波震级M_S,基于1范数线性回归(SR1和SR2)和2范数正交回归(OR)方法建立M_L与M_S间的转换关系。同时,对每个点采用高斯随机扰动后发现,高斯扰动前后近震震级与面波震级间的转换关系变化不大。结果显示,正交回归方法(OR)得到的曲线,均方根误差最小,为最佳拟合曲线,转换关系式为M_(S,内蒙)=0.96M_L-0.10。郭履灿震级转换关系M_S=1.13M_L-1.08与本文得到的转换关系存在明显系统偏差,这可能是由于区域构造特征差异所致。M_(S,内蒙)值明显大于M_(S,经验)值,平均差值为0.23,建议使用重新矫正的M_L与M_S转换关系式,M_(S,经验)与M_(S,内蒙)差值数量分布情况显示,差值为0.2~0.3的地震数量最多。 相似文献
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12002年12月14日玉门MS5.9地震发震时间:21∶27′27″;经纬度:39.8°N,97.3°E;深度:33km;震级:MS5.9。收集了全省及邻近省份共同31个台站初动后作出震源机制解(表1,图1)。表1 玉门MS5.9地震震源参数节面A节面BP轴T轴N轴矛盾比/%走向倾角滑动角走向倾角滑动角方位角仰角方位角仰角方位角仰角147°26°35°24°75°111°277°27°140°55°18°21°0.09722003年10月25日民乐-山丹MS6.1地震发震时间:20∶41′36.4″;经纬度:38.33°N,100.95°E;深度:12km;震级:MS6.1。收集了全省21个台站初动后作出震源机制解(表2,图2)。表2 民乐-山… 相似文献
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Using 116 earthquakes over M_L3.8 in the Inner Mongolia region from 2008 to 2015, the local earthquake magnitude M_L and surface wave magnitude M_S are remeasured. Based on norm linear regression(SR1 and SR2) and norm(OR) orthogonal regression method, we established the conversion relationship between M_L and M_S. The results were tested with Gaussian disturbance. The result shows that the orthogonal regression method(OR) result has the best fitting curve, and the conversion relation is M_S=0.96 M_L-0.10. The difference between our result and Guo Lücan's(M_S=1.13 M_L-1.08) may be caused by regional tectonic characteristics. M_(S Inner Mongolia) value is significantly higher than the M_(S empirical) value, with an average difference of 0.23, the difference distribution of empirical relation and the rectified relation is in the range of 0.2-0.3. 相似文献