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1.
— Based on the theory of LURR and its recent development, spatial and temporal variation of Y/Y c (value of LURR/critical value of LURR) in the Southern California region during the period from 1980 through March, 2001 was studied. According to the previous study on the fault system and stress field in Southern California, we zoned the Southern California region into 11 parts in each of which the stress field is almost uniform. With the time window of one year, time moving step of three months, space window of a circle region with a radius of 100 km and space moving step of 0.25 degree in latitude and longitude direction, the evolution of Y/Y c were snapshot. The scanning results show that obvious Y/Y c anomalies occurred before 5/6 of strong earthquakes considered with a magnitude of 6.5 or greater. The critical regions of Y/Y c are near the epicenters of the strong earthquakes and the Y/Y c anomalies occur months to years prior to the earthquakes. The tendency of earthquake occurrence in the California region is briefly discussed on the basis of the examination of Y/Y c .  相似文献   

2.
Understanding the relationship between precursory deformation anomalies and strong earthquakes is vital for physical earthquake prediction. Six months before the 2021 MS7.4 Maduo earthquake in Qinghai province, China, the vertical pendulum at the Songpan station was observed to tilt southward with a high rate and large amplitude. Studies conducted before the 2021 MS7.4 Maduo earthquake inferred the tilt anomaly to be an earthquake precursor. However, after the earthquake, the relation between the earthquake and the anomaly became controversial, partly because the Songpan station is located at a great distance from the epicenter. In this study, based on the deformation anomaly characteristics, relationship between the seismogenic fault and the fault near the anomaly, and associated quantitative analyses, we concluded that this anomaly may be associated with the 2021 MS7.4 Maduo earthquake. The duration and amplitude of this anomaly matched with the magnitude and epicenter distance of the Maduo earthquake. We have also interpreted the reason why the anomaly occurred near a fault that is obliquely intersected with the seismogenic fault and why the anomaly is located far from the earthquake epicenter.  相似文献   

3.
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   

4.
邢台5．4级地震前的流动重力和地磁异常初步研究   总被引：1，自引：0，他引：1  
根据测值空间变化等值线和时序变化曲线,分析了2002年邢台5．4级地震前流动重力和流动地磁异常的动态演化。两种异常震前表现出如下特征：①流动重力、流动地磁观测资料均有较为明显的前兆异常反应;②地震发生在重力变化的“0”等值线附近;③流动地磁部分点位测值呈现趋势性异常,震前全部点位观测值整体上升,形成完整的高值异常区。  相似文献   

5.
李鸿宇  王维  袁桂平 《中国地震》2018,34(2):364-370
使用江苏地区9个地磁台站2009年1月~2016年10月的分钟值数据,计算得到各台站的地磁谐波振幅比时间序列变化曲线。分析发现,2012年7月20日高邮4.9级地震、2016年10月20日射阳4.4级地震前,高邮台和盐城台地磁谐波振幅比YZH_x和YZH_y分别出现了长短周期不同步的异常变化。其异常特征表现为:(1)异常的长期变化形态为"下降—转折—恢复",在恢复过程中出现不同步现象,异常持续时间近3年,异常幅度为0.02~0.17;(2)YZH_y向的异常幅度大于YZH_x向,同时,2次地震主震的主压应力方向为EW向,存在异常幅度较大方向与主压应力方向一致的特点。  相似文献   

6.
运用地磁加卸载响应比方法(LURR)对华北地区23个地磁台站2008—2014年的数字化地磁相对记录数据进行计算分析,结果显示华北地区7年内发生了38次共计10组加卸载响应比异常,其中7组有震例对应,在选定的24次震例中16次有震前异常。经统计发现各次异常发生时其异常面积与最大异常强度成正比关系,各组异常内累计异常台站数量与组内地震辐射能量有一定相关性。对有震例的7组异常分析后认为多数情况下组内各次异常之间有一定联系,主要表现为位置的连续性及继承性,并且发现震中位置和异常位置分布有一定关系。  相似文献   

7.
分析了乌恰5．7级地震前喀什-乌恰地区的地震活动情况和地震学参数异常过程。研究认为，5．7级地震发生在1996年9月以来形成的喀什西南4．0级以上地震空区的边缘，此次地震的活动间隔时间为1980年以来之最；震前有6项地震学参数空间扫描和5项地震学参数时间进程存在中短期异常；震前3级地震活动强度有多次起伏。  相似文献   

8.
Water levels have been monitored in wells along the San Jacinto fault zone since 1977. The three largest earthquakes to occur within 30 km of the segment of the San Jacinto fault zone being monitored with continuous recorders showed magnitudesM of 4.5, 4.8, and 5.5. Two wells in Borrego Valley, 31 to 32 km southeast of theM=5.5 earthquake on 25 February 1980, showed anomalous spikes recording a probable strain event 88 hours before the earthquake. Two other wells 12 km northwest of the epicenter showed no water-level anomalies. No water-level anomalies preceded theM=4.8 earthquake near Anza on 15 June 1982. Anomalous water-level fluctuations occurred in a well near Ocotillo Wells, 13 km northeast of theM=4.5 earthquake on 22 March 1982, 19 to 23 days prior to the earthquake. Similar fluctuations in other wells have not been followed by sizable earthquakes. A simultaneous drop in water level occurred in four wells on 8 September 1982; this possible strain event was not associated with a sizable earthquake. The presumed strain events occur only in wells that show earth tides and may have been the result of creep on strands of the San Jacinto fault zone. Although water-level anomalies have occurred in only one or two wells prior to two out of three moderate (M=4.5–5.5) earthquakes, the simultaneous drop in water level on 8 September 1982 and the spikes in two wells before theM=5.5 earthquake on 25 February 1980 suggest that wells responsive to earth tides may detect strain events.  相似文献   

9.
利用云南11个地磁台站的秒采样观测数据,计算和分析了地磁垂直强度极化值Yzh在2019年8月13日、14日通海MS5.0地震前及2019年9月8日墨江MS5.9地震前的时空变化特征。研究表明,地磁台站Yzh值的幅度在震前会出现同步增强现象。而与以往的极化震例研究相比,Yzh值的高值异常在震前出现时间要更早些,可能会在震前2~5个月出现,距发震时间越近,产生的异常幅值可能越大,异常持续时间也越长。同时,研究还发现2次地震主要发生在异常空间等值线的高值区内,尤其在零值阈值线附近,这可能对今后发震地点的预测有一定的指示意义。对比异常产生时段内的Dst指数,认为该高值异常并非由空间电流体系所引起。  相似文献   

10.
本文针对2015年4月15日发生在南北地震带北端的阿拉善左旗5.8级地震,利用乌海台、东升庙台、石嘴山台的连续数字地震波形资料,采用快速傅里叶变换对三个台站的2015年4月1日00时—4月15日23时波形数据进行分析,并持续跟踪0~0.25 Hz包络幅值极大值的变化形态。结果显示:(1)在5.8级地震前,震中附近的乌海地震台、东升庙地震台、石嘴山地震台记录的地震波形均出现频谱向低频偏移的现象;(2)三个台站出现低频异常的包络幅值极大值跟踪形态不一致,其中只有乌海台在震前出现明显的持续不稳定异常,异常持续时间约120h;(3)三个台站距离震中由近及远包络幅值极大值的跟踪形态差异明显。  相似文献   

11.
选取新疆地区2016年以来发生的3次MS 6.0以上浅源地震,对发震前震中区小震调制比变化进行系统对比分析,发现3次地震前均出现不同程度的固体潮调制比异常：①2016年12月8日呼图壁MS 6.2地震仅在震前2年于震中出现调制比高值异常;②2017年8月9日精河MS 6.6地震震中于发生前2年、1年、0.5年均落于调制比高值异常区域,受调制作用较明显;③2020年1月19日伽师MS 6.4地震于发生前2年、1年,在震中位置附近出现调制比异常。  相似文献   

12.
基于GM4磁通门磁力仪秒数据,分析研究了2008-2014年天水地磁台的地磁极化值和转换函数变化,结果表明在2013年岷县6.6级地震前天水台地磁极化值和转换函数存在不同程度的异常：（1）转换函数|A|和|B|在震前均出现了下降-转折-上升的异常变化,在上升至最高点时发生了岷县6.6级地震;（2）较短的周期转折上升变化更明显,幅度也更大,如|A|的20~80 s和|B|的20~110 s;（3）3.20 s、50 s和80 s周期的帕金森矢量方位角在震前出现转向并指向震中的现象;（4）4.5~100 s周期的极化值Yzh在震前3个月出现2次超3倍均方差的高值异常。  相似文献   

13.
Lushan MS7.0 earthquake occurred in Lushan county, Ya'an city, Sichuan province of China, on 20 April 2013, and caused 196 deaths, 23 people of missing and more than 12 thousand of people injured. In order to analyze the possible seismic brightness temperature anomalies which may be associated with Lushan earthquake, daily brightness temperature data for the period from 1 June 2011 to 31 May 2013 and the geographical extent of 25°E-35°N latitude and 98°E-108°E longitude are collected from Chinese geostationary meteorological satellite FY-2E. Continuous wavelet transform method which has good resolution both in time and frequency domains is used to analyze power spectrum of brightness temperature data. The results show that the relative wavelet power spectrum (RWPS) anomalies appeared since 24 January 2013 and still lasted on 19 April. Anomalies firstly appeared at the middle part of Longmenshan fault zone and gradually spread toward the southwestern part of Longmenshan fault. Anomalies also appeared along the Xianshuihe fault since about 1 March. Eventually, anomalies gathered at the intersection zone of Longmenshan and Xianshuihe faults. The anomalous areas and RWPS amplitude increased since the appearance of anomalies and reached maximum in late March. Anomalies attenuated with the earthquake approaching. And eventually the earthquake occurred at the southeastern edge of anomalous areas. Lushan earthquake was the only obvious geological event within the anomalous area during the time period, so the anomalous changes of RWPS are possibly associated with the earthquake.  相似文献   

14.
After using the "Time-Frequency Relative Power Spectrum" (T-F RPS) method based on the China Geostationary Meteorological Satellite (FY-2C/FY-2E) infrared remote sensing brightness temperature data processing, we rapidly and accurately extracted and identified pre-earthquake thermal infrared anomalies for the April 16, 2013 MW7.8 of Khash, Iran Earthquake. Spatial evolution of anomalies showed the distribution and process. The anomalies were mainly distributed in the east of Khash,Iran.The characteristics of process and distribution presented X-Type model of NE and near NS strip which relates to the geological structure of this region. The epicenter was located near the intersection region of the X-Type abnormal migration process. Besides, the results of time series of anomalies showed that, the duration was more than 40 days and the maximum amplitude was about 18 times. The earthquake occurred 20 days after the abnormal maximum amplitude which appeared on March 26, 2013.  相似文献   

15.
The Tohoku megathrust earthquake, which occurred on March 11, 2011 and had an epicenter that was 70 km east of Tohoku, Japan, resulted in an estimated ten's of billions of dollars in damage and a death toll of more than 15 thousand lives, yet few studies have documented key spatio-temporal seismogenic characteristics. Specifically, the temporal decay of aftershock activity, the number of strong aftershocks (with magnitudes greater than or equal to 7.0), the magnitude of the greatest aftershock, and area of possible aftershocks. Forecasted results from this study are based on Gutenberg-Richter's relation, Bath's law, Omori's law, and Well's relation of rupture scale utilizing the magnitude and statistical parameters of earthquakes in USA and China (Landers, Northridge, Hector Mine, San Simeon and Wenchuan earthquakes). The number of strong aftershocks, the parameters of Gutenberg-Richter's relation, and the modified form of Omori's law are confirmed based on the aftershock sequence data from the MW9.0 Tohoku earthquake. Moreover, for a large earthquake, the seismogenic structure could be a fault, a fault system, or an intersection of several faults. The seismogenic structure of the earthquake suggests that the event occurred on a thrust fault near the Japan trench within the overriding plate that subsequently triggered three or more active faults producing large aftershocks.  相似文献   

16.
The El Mayor-Cucapah earthquake sequence started with a few foreshocks in March 2010, and a second sequence of 15 foreshocks of M?>?2 (up to M4.4) that occurred during the 24?h preceding the mainshock. The foreshocks occurred along a north?Csouth trend near the mainshock epicenter. The M w 7.2 mainshock on April 4 exhibited complex faulting, possibly starting with a ~M6 normal faulting event, followed ~15?s later by the main event, which included simultaneous normal and right-lateral strike-slip faulting. The aftershock zone extends for 120?km from the south end of the Elsinore fault zone north of the US?CMexico border almost to the northern tip of the Gulf of California. The waveform-relocated aftershocks form two abutting clusters, each about 50?km long, as well as a 10?km north?Csouth aftershock zone just north of the epicenter of the mainshock. Even though the Baja California data are included, the magnitude of completeness and the hypocentral errors increase gradually with distance south of the international border. The spatial distribution of large aftershocks is asymmetric with five M5+ aftershocks located to the south of the mainshock, and only one M5.7 aftershock, but numerous smaller aftershocks to the north. Further, the northwest aftershock cluster exhibits complex faulting on both northwest and northeast planes. Thus, the aftershocks also express a complex pattern of stress release along strike. The overall rate of decay of the aftershocks is similar to the rate of decay of a generic California aftershock sequence. In addition, some triggered seismicity was recorded along the Elsinore and San Jacinto faults to the north, but significant northward migration of aftershocks has not occurred. The synthesis of the El Mayor-Cucapah sequence reveals transtensional regional tectonics, including the westward growth of the Mexicali Valley and the transfer of Pacific?CNorth America plate motion from the Gulf of California in the south into the southernmost San Andreas fault system to the north. We propose that the location of the 2010 El Mayor-Cucapah, as well as the 1992 Landers and 1999 Hector Mine earthquakes, may have been controlled by the bends in the plate boundary.  相似文献   

17.
对祁连山地震带1991—2004年间发生的13次中强地震,采用NOAA卫星热红外遥感资料数据库进行地面温度的时空网格化扫描,获得多年连续的热红外时序,研究地震前后的温度演化过程,提取震前地表温度的异常特征。研究结果表明,有38%的地震在震前出现了热红外异常现象,有的表现为温度降低,有的则表现为温度升高,体现了地震诱发因素的复杂性;温度异常幅度均为2~3℃,异常出现的时间均在2个月内;震级越大,异常越明显,但并非所有6级以上地震都比5~6级地震的热红外异常明显。  相似文献   

18.
This paper introduces relative and absolute gravity change observations in the eastern portion of the Tibetan Plateau. We analyze and discuss a change that occurred in 2010 in the gravity along the eastern margin of the plateau and the relationship between this change and the 2013 Lushan M S7.0 earthquake. Our results show that: (1) before the Lushan M S7.0 earthquake, gravity anomalies along the eastern margin of the Tibetan Plateau changed drastically. The Lushan earthquake occurred at the bend of the high gradient zone of gravity variation along the southern edge of the Longmenshan fault zone. (2) The 2013 Lushan earthquake occurred less than 100 km away from the epicenter of the 2008 Wenchuan earthquake. Lushan and Wenchuan are located at the center of a four-quadrant section with different gravity anomalies, which may suggest that restoration after the Wenchuan earthquake may have played a role in causing the Lushan earthquake. (3) A medium-term prediction based on changes in gravity anomalies was made before the Lushan M S7.0 earthquake, in particular, a prediction of epicenter location.  相似文献   

19.
基于甘青川地区的14个地磁台站秒采样资料,对2022年1月8日青海门源MS6.9地震前地磁垂直强度极化异常的时空变化特征进行分析研究。计算结果显示,在2021年10月底出现了地磁极化超阈值高值异常变化,异常台站主要分布在青海、甘肃和四川地区,异常出现后73天发生了门源地震,震中位于极化高值异常阈值线附近。研究还发现,此次地磁极化异常具有一定的时空变化特征,时间上,不同台站极化异常具有较好的时间同步性;空间上,极化异常高值区呈现出沿震中附近出现后不断扩展最终再向震中收缩的特点。此外,各地磁极化异常台站的归一置零极化值、异常持续时间与震中距存在较好的负相关性,异常台站距离地震震中越近,其归一置零极化值越高,异常持续时间也越长,这一特征符合地震电磁扰动信号的衰减特征。根据极化异常和地震的时空关系分析认为,此次地磁极化高值异常对应了之后在异常高值区边缘发生的门源MS6.9地震。  相似文献   

20.
丁志华  崔月菊  唐杰 《中国地震》2022,38(3):494-502
基于高光谱遥感数据,通过RST算法提取2020年7月12日唐山5.1级地震前不同参数异常信息,发现震前CH4、CO、H2O、O3均出现了高值异常,且异常均位于震中附近,异常幅度高于2倍均方差,CH4、CO、H2O异常机理不同于O3。通过统计2018—2020年CH4、CO、H2O三种气体出现频次,发现同步异常具有可靠性,认为高光谱多参数异常出现的同步性,可提高异常性质判定的信度。通过对不同参数进行连续跟踪观测,提取多参数同步异常信息,对地震短临预报具有一定参考意义。  相似文献   

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