共查询到19条相似文献，搜索用时 298 毫秒
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利用相对功率谱方法对风云卫星热红外亮温数据进行处理，发现精河MS6.6地震前存在明显的前兆异常。异常时空演化特征为2017年7月12日在北天山地震带中、东部和阿尔泰地震带中部开始出现相对功率谱高值聚集现象，随后幅值和面积逐渐增大，持续至7月27日异常面积和幅度达到最大值，然后逐渐减弱，2017年8月14日后基本恢复正常，异常持续大约1个月，8月9日在异常区域边缘发生精河MS6.6地震。地震震中所在的北天山地震带平均相对功率谱值时序变化特征与异常区域时间演化过程类似，地震发生在平均相对功率谱由最大值恢复至正常背景值的过程中。 相似文献
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2017年8月9日精河发生MS6.6地震，随后发生一系列余震。本文采用PTD方法和新疆测震台网分析的震相数据，基于新疆“2015地壳速度模型”，计算了该地震序列的震源深度，得到MS6.6主震震源深度约为14km，MS≥2.5余震深度为9～18km。所有震相数据来自中国地震台网中心编目数据库。 相似文献
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基于新疆区域数字地震台网震相观测报告，采用HypoDD方法精确定位了精河MS6.6地震序列ML≥1.0地震的震源位置，综合分析了此次地震序列的空间分布特征和可能的发震构造。结果显示，主震震中为44.2639°N、82.8294°E，震源初始破裂深度为17.6km；地震序列总体沿近EW（273°）向单侧扩展，展布长度约20km；震源深度优势分布范围为7～17km；沿余震走向的深度剖面显示，主震向西10km范围内，余震震源有逐渐变浅的趋势，余震序列中尾端向SW方向偏转的地震震源较深；垂直于地震序列的深度剖面显示，地震序列自北向南呈现逐渐加深的变化特征，表明发震断层面倾向为S倾。综合考虑中国地震局地球物理研究所给定的震源机制解以及震源区地质构造情况推测，精河MS6.6地震发震构造可能为库松木契克山前断裂东段。 相似文献
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在中国地震台网中心2016年底利用热红外遥感技术预测2017年新疆西部地区为潜在MS 6.6±0.2地震危险区的基础上，分析2017年8月9日精河MS6.6地震临震时段引潮力变化，并选用18时（UTC）中国大陆近地表50m高度处的遥感大气温度数据，以震前引潮力值最高点时刻（8月1日）为时间背景，获取地震前后（8月2~13日）连续的大气温度日增量分布图像，跟踪分析精河MS6.6地震短临大气温度变化。结果显示：地震发生在天体引潮力由高峰—低谷连续周期变化的低谷时段，而大气温度变化过程显示，在全国大范围内，仅震中附近大气温度升高明显，其异常演化经历了起始—加强—高峰—衰减—再增强—发震—平静的动态过程。增温过程与潮汐变化具有同步性，这表明引潮力对本次地震具有触诱发的作用，而大气温度变化反映了本次地震地应力的变化过程，也说明在地震预测实践中，从中、短临多时间尺度综合分析遥感大气温度和引潮力变化，将有助于提高地震预测能力。 相似文献
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2018年9月4日新疆伽师发生MS5.5地震，震中处于塔里木地块西北缘，位于1997~1998年伽师强震群震区内。此次伽师地震前发生了MS4.7前震，截至9月30日最大余震震级为MS4.6（ML5.0），初步判定为前-主-余型地震序列。序列精定位结果显示，余震沿近NE向展布，主震震源深度与1997~1998年伽师强震主震基本一致，发震断层陡立。本文从区域的构造环境、地震震源机制解和余震分布特征等方面分析认为，地震发生在伽师隐伏断裂东南端部，为1997~1998年伽师强震群震区的一次新的构造活动。序列参数、视应力等计算结果显示，伽师MS5.5地震的预测最大余震震级与最大余震震级MS4.6接近，表明序列最大余震已经发生。 相似文献
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利用甘肃省区域台网提供的地震波形资料，计算甘肃南部地区2010年1月～2017年8月ML≥2.0地震的视应力，分析九寨沟地震前甘南地区视应力的时空演化特征，所得结果如下：①ML2.6～3.1、ML2.0～2.5震级段地震视应力的空间分布具有较好的一致性，九寨沟MS7.0地震前，距震中较近的川甘交界地区的舟曲、文县等地呈现出较为集中的视应力高值异常；②ML2.0～2.5、ML2.6～3.1地震的视应力在大区域范围内随时间的变化趋势有一定差异，ML2.6～3.1地震视应力变化更为明显，在较大区域范围内表现为震前显著升高，而ML2.0～2.5地震视应力则在震前一两年内开始下降；③随着区域划分范围向震中靠近，ML2.0～2.5、ML2.6～3.1地震视应力的变化逐渐趋于一致，至震中附近时，2个震级段视应力均表现为“震前几年长时间升高—临震前几个月下降”的同步变化。 相似文献
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利用新疆地区北疆测网2015～2017年观测的共4期流动重力资料，分析研究区半年、1年尺度重力变化特征，并采用小波分解方法，对2017年8月9日精河MS6.6地震前重力变化异常进行分解，分离了不同深度的重力异常。结果表明，震中附近的精河地区从2015年开始一直处于重力负值变化，同时，震中周围的重力正值变化集中区逐步向震中地区迁移，地震发生前震中以南60km处出现重力变化零值线，并且零值线两侧的重力累积变化量达到70μGal。小波分解后，4阶细节图较好地反映了精河地震前的重力异常，其与地震孕育发生有较好的对应性。 相似文献
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2022年1月8日青海省海北州门源县发生MS6.9地震,震中距离2016年1月21日门源MS6.4地震震中约33km,两次门源地震均发生在冷龙岭断裂附近,但在震源机制、主发震断层破裂过程及地震序列余震活动等方面显著不同。针对两次门源地震序列的比较分析,对研究冷龙岭断裂及其附近区域强震序列和余震衰减特征等具有重要研究意义。通过对比分析2022年门源MS6.9地震和2016年门源MS6.4地震余震的时空演化特征,发现二者在震源过程和断层破裂尺度上存在明显差异,前者发震断层破裂充分,震后能量释放充分,余震丰富且震级偏高;而后者发震断层未破裂至地表,余震震级水平偏低。综合分析两次门源地震序列表现出来的差异性,认为其可能与地震发震断层的破裂过程密切相关,且同时受到区域构造环境的影响。 相似文献
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分析距离九寨沟MS7.0地震震中分别为65 km、254 km和238 km的松潘地磁台、成都地磁台和天水地磁台2017年连续观测结果,发现九寨沟地震前,松潘地磁台出现异常变化,主要表现为2017年5月开始,松潘地磁台长时间垂直分量累积变化量达40 nT。短时间内也存在地磁场突变,最高可达10 nT,而成都地磁台和天水地磁台地磁场无明显异常。通过对观测数据的详细检查发现松潘地磁台很多观测日的最后一个观测值与后一观测日的第一个观测值相差超过1 nT,因此认为九寨沟地震前观测数据的异常是由观测系统异常导致。对三个台站地磁场垂直分量日变化的统计分析发现垂直分量在不同时段相关性保持一致,说明地震前短时间内不存在地磁垂直分量的明显异常变化,三个台站地磁场日变化的差异是由地下介质性质不同导致。岩石圈磁场在震中西侧区域出现正负异常交替现象,这可能与九寨沟地震的孕育有关。 相似文献
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近年来,地磁谐波振幅比方法在国内得到较广泛的应用,并成为一种较为有效的地震预测方法。本文利用谐波振幅比方法,对2017年11月23日重庆武隆5.0级地震震中附近台站的地磁三分量数据进行计算,并分析了各台站10~60min周期谐波振幅比值异常特征。研究发现,异常台站几乎均位于震源机制解的拉张区(P波向下的区域),具有象限分布特征;异常台站NS向谐波振幅比值变化存在分层现象,短周期(浅部)的变化与长周期(深部)变化成相反相位,从电磁学机理看,浅部与深部之间存在EW向的面电流;近震中台站的异常低点时间存在由长周期(深部)向短周期(浅部)迁移的现象。 相似文献
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针对高邮-宝应4.9级地震发生前后附近地区未发生其它中等以上地震、地震事件孤立及周边地磁台站分布较密有利于研究地震地磁异常时空特征的特点,较为系统地分析总结了该地震发生前后地磁谐波振幅比的变化特征,研究结果进一步验证了目前对地磁谐波振幅比异常特征的认识,即地磁谐波振幅比异常特征表现出与地电阻率类似的下降-转折-恢复上升的异常变化过程,地震一般发生在异常转折或恢复上升过程中,距震中较近的台站会出现不同步现象——南北向与东西向的不同步以及长短周期的不同步。 相似文献
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Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang MS6.1 earthquake and the Ludian MS6.5 earthquake in 2014. We processed the geomagnetic vertical component diurnal variation data by the spatial correlation method. The results show that during the period from April 1 to May 20, 2014,there existed quasi-synchronous decrease changes in the coefficient curves between the five geomagnetic stations of Guiyang,Hechi,Nanshan,Muli,Yongning and Xinyi and Hongshan stations.Furthermore,there was a high gradient zone in the normalized correlation coefficient contour map with background values removed. The epicenters of the Yingjiang MS6.1 earthquake and the Ludian MS6.5 earthquake are located in the gradient zone or near the gradient zone. 相似文献
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The hourly averaged Polar Cap (PC) index was used as the input parameter for the ring current index Dst variation forecasting. The PC index is known to describe well the principal features of the interplanetary magnetic field as well as the total energy input to the magnetosphere. This allowed us to design a neural network that was able to forecast the Dst variations 1 h ahead. 1995 PC and Dst data sets were used for training and testing and 1997 data sets were used for validation. From 15 moderate and strong geomagnetic storms observed during 1997, 10 were successfully forecasted. In 3 cases the observed minimum Dst value was less than the predicted value, and only in 3 cases the neural network was not able to reproduce the features of the geomagnetic storm. 相似文献
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The secular variations (SV) ing
1
0
of geomagnetic field, caused by the interaction between the geomagnetic field and the radial fluid-flow of the outer-core,
are discussed with both statistical and analytic methods. When the value ofg
1
0
s
2
0
is relatively high compared with other terms, SV ing
1
0
is characterized by exponential change. When the effect of non-dipole field is notable, SV ing
1
0
shows complex features. Especially when the value of g
1
0
is close to zero, SV ing
1
0
is completely determined by the random process of non-dipole fields.
Project supported by the National Natural Science Foundation of China (Grant No. 49429405) and by the Chinese Academy of Sciences. 相似文献
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785 traces of vertical components from shallow earthquakes recorded by 10 CDSN (Chinese Digital Seismographic Network) stations
and 5 GSN (Global Seismographic Network) stations were collected to study the attenuation characteristics ofL
g coda in the Chinese continent and its adjacent regions. The records were processed first using the stack spectral ratio method
to obtain the average values ofQ
0 (Q at 1Hz) and η, the frequency dependence, ofL
g coda in the ellipses corresponding to the paths. The back-projection technique was then employed to obtain the tomographic
maps ofQ
0 and η values, and the distribution of their errors. Results indicate that in the studied areaQ
0 varies between 200 and 500. The lowest value ofQ
0 exists in the Yun-nan-Tibetan region, while the highest value ofQ
0 occurs in the southern edge of Siberian platform. η varies between 0.3 and 0.8. For most part of the studied area η varies
inversely withQ
0. 相似文献
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Victor U. Chukwuma 《Acta Geophysica》2007,55(4):469-489
A study of the geomagnetic storm of July 13–14, 1982, and its ionospheric response is presented using the low-latitude magnetic
index, Dst, and interpreted using solar wind interplanetary data: proton number density, solar wind flow speed, interplanetary magnetic
field southward component B
Z
, and solar wind dynamic pressure. The F2 region structure response to the geomagnetic storm was studied using foF2 data obtained during the storm from a network of various ionosonde stations. Our results appear to show simultaneous abrupt
depletion of foF2 that occurred at all latitudes in both the East Asian and African/European longitudinal zone during the period: 18:00–19:00
UT on July 13 and is as result of an abrupt increase in the dynamic pressure between 16:00 and 17:00 UT. The dynamic pressure
increased from 3.21 to 28.07 nPa within an hour. The aforementioned abrupt depletion of foF2 simultaneously resulted in an intense negative storm with peak depletion of foF2 at about 19:00 at all the stations in the East Asian longitudinal zone. In the African/European longitudinal zone, this simultaneous
abrupt depletion of foF2 resulted in intense negative storm that occurred simultaneously at the low latitude stations with peak depletion at about
20:00 UT on July 13, while the resulting negative storm at the mid latitude stations recorded peak depletion of foF2 simultaneously at about 2:00 UT on July 14. The present results indicate that most of the stations in the three longitudinal
zones showed some level of simultaneity in the depletion of foF2 between 18:00 UT on July 13 and 2:00 UT on July 14. The depletion of foF2 during the main phase of the storm was especially strongly dependent on the solar wind dynamic pressure. 相似文献
19.
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