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1.
2019年6月17日四川长宁发生MS6.0地震, 之后发生了一系列的强余震, 为更好地分析此次地震的序列特征以及强余震的可预测属性, 采用国际上对复杂序列拟合相对较好的“传染型余震序列”(ETAS)模型以及基于Reseanberg-Jones(R-J)模型发展的Omi-R-J模型, 通过连续滑动、 拟合和余震发生率预测, 对地震序列的模型参数稳定性、 预测结果进行了比较研究, 并利用N-test、 T-test检验方法对预测结果进行了效能评估。 结果表明, 相比于其他中强震序列参数, 此次长宁MS6.0地震序列参数中反映激发能力的αETAS较其他序列明显偏小, 而反映衰减能力的pORJ值和应力累积水平的bORJ值相对较小, 与此次余震序列丰富、 持续时间相对较长相吻合; ETAS和Omi-R-J模型对于复杂序列在[3.0, 3.5, 4.0]三个震级档的强余震仍具有一定的预测能力; 总体的“每个地震的信息增益”(IGPE)计算结果显示, ETAS模型略优于Omi-R-J模型, 前者或更适合复杂地震序列的余震预测。 相似文献
2.
Data replenishment of five moderate earthquake sequences in Japan,with semi-automatic cluster selection 
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下载免费PDF全文 Missing early aftershocks following relatively large or moderate earthquakes can cause significant bias in the analysis of seismic catalogs. In this paper, we systematically address the aftershock missing problem for five earthquake sequences associated with moderate-size events that occurred inland Japan, by using a stochastic replenishing method. The method is based on the notion that if a point process (e.g., earthquake sequence) with time-independent marks (e.g., magnitudes) is completely observed, it can be transformed into a homogeneous Poisson process by a bi-scale empirical transformation. We use the Japan Meteorological Agency (JMA) earthquake catalog to select the aftershock data and replenish the missing early events using the later complete part of each aftershock sequence. The time windows for each sequence span from 6 months before the mainshock to three months after. The semi-automatic spatial selection uses a clustering method for the epicentral selection of earthquakes. The results obtained for the original JMA catalog and replenished datasets are compared to get insight into the biases that the missing early aftershocks may cause on the Omori-Utsu law parameters’ estimation, characterizing the aftershock decay with time from the mainshock. We have also compared the Omori-Utsu law parameter estimates for two datasets following the same mainshock; the first dataset is the replenished sequence, while the second dataset has been obtained by waveform-based analysis to detect early aftershocks that are not recorded in the JMA catalog. Our results demonstrate that the Omori-Utsu law parameters estimated for the replenished datasets are robust with respect to the threshold magnitude used for the analyzed datasets. Even when using aftershock time windows as short as three days, the replenished datasets provide stable Omori-Utsu law parameter estimations. The p-values for all the analyzed sequences are about 1.1 and c-values are significantly smaller compared to those of original datasets. Our findings prove that the replenishment method is a fast, reliable approach to address the missing aftershock problem. 相似文献
3.
《地震研究进展（英文）》2023,3(1):100184
The 2022 MS 6.8 Luding earthquake is the strongest earthquake in Sichuan Province, Western China, since the 2017 MS 7.0 Jiuzhaigou earthquake. It occurred on the Moxi fault in the southeastern segment of the Xianshuihe fault, a tectonically active and mountainous region with severe secondary earthquake disasters. To better understand the seismogenic mechanism and provide scientific support for future hazard mitigation, we summarize the preliminary results of the Luding earthquake, including seismotectonic background, seismicity and mainshock source characteristics and aftershock properties, and direct and secondary damage associated with the mainshock. The peak ground displacements in the NS and EW directions observed by the nearest GNSS station SCCM are ～35 mm and ～55 mm, respectively, resulting in the maximum coseismic dislocation of 20 mm along the NWW direction, which is consistent with the sinistral slip on the Xianshuihe fault. Back-projection of teleseismic P waves suggest that the mainshock rupture propagated toward south-southeast. The seismic intensity of the mainshock estimated from the back-projection results indicates a Mercalli scale of VIII or above near the ruptured area, consistent with the results from instrumental measurements and field surveys. Numerous aftershocks were reported, with the largest being MS 4.5. Aftershock locations (up to September 18, 2022) exhibit 3 clusters spanning an area of 100 km long and 30 km wide. The magnitude and rate of aftershocks decreased as expected, and the depths became shallower with time. The mainshock and two aftershocks show left-lateral strike-slip focal mechanisms. For the aftershock sequence, the b-value from the Gutenberg-Richter frequency-magnitude relationship, h-value, and p-value for Omori’s law for aftershock decay are 0.81, 1.4, and 1.21, respectively, indicating that this is a typical mainshock-aftershock sequence. The low b-value implies high background stress in the hypocenter region. Analysis from remote sensing satellite images and UAV data shows that the distribution of earthquake-triggered landslides was consistent with the aftershock area. Numerous small-size landslides with limited volumes were revealed, which damaged or buried the roads and severely hindered the rescue process. 相似文献
4.
利用此次伽师地震序列震相数据,通过走时曲线得到震源区的初始一维速度模型。结合此速度模型,利用单纯形法测定了新疆伽师M S6.4地震参数。使用双差定位方法对伽师地震和M L≥1.8的297次余震事件进行了重新定位,得到结论:①伽师M S6.4地震参数为39.841°N、77.151°E、深度14.4 km。②伽师地震的破裂是非均匀、迁移的。主、余震整体分布呈“T”字型展布,主震位于“T”字底部,“T”字的横长竖短,多数余震向主震的正北方向延伸,余震整体呈近东西方向展布,东西方向长约40 km,南北方向长约20 km。前震、主震发生在震源区近南面的隐伏断层,可能是受塔里木盆地的阻碍,余震并没有向南发展,而是逐渐向北延伸至位于北面的隐伏断层,后又沿北面的断层向东发展。③通过序列整体分布呈“T”字型展布,初步判断伽师地震是一次共轭断层破裂事件。余震一边向主震正北方向发展,一边继续向东发展,表明发震断层是一条近EW向北倾断层,同时证明了塔里木盆地向北插入南天山。④地震震源深度主要集中在10~20 km,占73%,优势破裂深度在中地壳,中地壳积累和释放的能量居多。伽师地震位于塔里木盆地边缘,地表覆盖有7~8 km的低速沉积层。 相似文献
5.
We obtained a catalog of early aftershocks of the 2013 Lushan earthquake by examining waveform from a nearby station MDS which is 30.2 km far away from the epicenter, and then we analyzed the relation between aftershock rate and time. We used time-window ratio method to identify aftershocks from continuous waveform data and compare the result with the catalog provided by China Earthquake Networks Center (CENC). As expected, a significant amount of earthquakes is missing in CENC catalog in the 24 h after the main shock. Moreover, we observed a steady seismicity rate of aftershocks nearly in the first 10,000 s before an obvious power-law decay of aftershock activity. We consider this distinct early stage which does not fit the Omori law with a constant p (p ~ 1) value as early aftershock deficiency (EAD), as proposed by previous studies. Our study suggests that the main shock rupture process is different from aftershocks’ processes, and EAD can vary in different cases as compared to earthquakes of strike-slip mechanism in California. 相似文献
6.
Spatio-temporal characteristics of aftershocks and seismogenic structure of the 2011 MW9.0 Tohoku earthquake,Japan 下载免费PDF全文
下载免费PDF全文 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
7.
Forecasting aftershock activity: 1. Adaptive estimates based on the Omori and Gutenberg–Richter laws
The method for forecasting the intensity of the aftershock processes after strong earthquakes in different magnitude intervals is considered. The method is based on the joint use of the time model of the aftershock process and the Gutenberg–Richter law. The time model serves for estimating the intensity of the aftershock flow with a magnitude larger than or equal to the magnitude of completeness. The Gutenberg–Richter law is used for magnitude scaling. The suggested approach implements successive refinement of the parameters of both components of the method, which is the main novelty distinguishing it from the previous ones. This approach, to a significant extent, takes into account the variations in the parameters of the frequency–magnitude distribution, which often show themselves by the decreasing fraction of stronger aftershocks with time. Testing the method on eight aftershock sequences in the regions with different patterns of seismicity demonstrates the high probability of successful forecasts. The suggested technique can be employed in seismological monitoring centers for forecasting the aftershock activity of a strong earthquake based on the results of operational processing. 相似文献
8.
大森-宇津定律的一种可能机制以唐山大地震为例 总被引：2，自引：0，他引：2
为了探讨大森-宇津定律的物理机制, 本文在余震区等效黏度远低于其外部, 且构造应力场在整个余震活动时间间隔内基本保持不变的假设条件下, 提出了一个开尔文黏弹性地震震源体概念模型． 该模型可用于模拟主震后断层蠕变和震源区应力调整触发的余震序列以及蠕变停止后余震终结、 介质恢复到弹性状态、 断层重新闭锁和积累下一次地震的整个过程． 有限元方法可用来计算非均匀黏弹性地震震源体模型中主震和每次余震所引起的应力场及其随时间的演化过程． 在此基础上, 采用开尔文黏弹性地震震源体概念模型和有限元方法模拟了1976年唐山MS7.8地震余震序列． 结果表明: 经验的大森-宇津定律可以用开尔文黏弹性震源体模型来解释, 这意味着余震衰减的频度取决于蠕变的速率; 余震序列持续时间受控于震源体的黏度, 即黏度越大, 蠕变时间越长, 余震持续的时间也就越长． 相似文献
9.
2001年MS8.1昆仑山口西地震和2008年MS8.0汶川地震发生在同一构造单元,但其余震序列无论在个数、空间分布,还是持续时间上都表现了显著的差别.余震通常由主震区域内背景场地震活动性受到的扰动所引起,这样的扰动则来自于主震造成的应力场状态的变化.本文从滑移速率和状态相依赖的摩擦定律(Rate- and State-Dependent Friction Law)出发,结合区域主震前后的地震活动性资料,定量地估算了这两个大地震后余震序列可能的持续时间,并对不同模型所得的结果进行了比较和对比.结果表明,汶川地震余震持续时间约为昆仑山口西地震余震持续时间的20倍,这是由于昆仑山口西地震和汶川地震余震序列的个数和持续时间不仅与地震成核过程的状态变化有关,还与作用在断层面上的正应力 σN 和剪应力加载速率 τ· 的大小有关.主震前后剪应力速率 τ· 的差别导致了在相同大小应力扰动ΔCFS之后的余震的活动性变化率的明显不同,导致了所触发的余震的个数和余震序列的持续时间的巨大差别.通过对昆仑山口西地震和汶川地震余震序列的时空分布特征和持续时间的定量化认识,可以为地震灾害定量评估提供合理和有益的物理参数. 相似文献
10.
为考察2013年4月20日芦山MS7.0地震震后序列参数的早期特征, 利用“传染型余震序列”(ETAS)模型和最大似然法进行了参数估计. 设定截止震级Mc=ML2.0, 拟合时段为震后0.31—24.12天, 计算获得α=1.89, p=1.22, 同时利用最大似然法估计获得b=0.72. 与中国大陆地区其它中强震的余震序列参数的比较表明, 芦山MS7.0地震序列参数表现为触发次级余震的能力较弱和序列衰减速率较快的特征, 反映出余震区相对较高的应力水平. 为检测结果的稳定性, 设定不同的截止震级Mc以及不同的拟合截止时间, 分别进行参数拟合和参数标准差估计. 结果表明, Mc的选取对α值影响明显, 对p值影响则较小. 此外, 震后10天内获得的参数拟合结果随时间变化较为明显, 而其后各参数变化总体较为平稳. 相似文献
11.
采用互相关系数法, 计算了2011年安庆MS4.8地震的余震S波分裂参数。 结果表明, 余震序列的S波分裂现象明显, 快S波平均偏振方向在近NNW向, 与区域最大水平主压应力方向基本一致。 通过分析延迟时间随时间的变化趋势, 可以看出MS4.8地震后有明显的应力释放现象。 在几次较大余震前, 观测到延迟时间呈现增加的特征, 并且其中一次余震在发生之前的短时间内还出现延迟时间减小的现象, 这一现象符合震前应力长时间积累和短时间应力释放的结论, 时间延迟在强震前会出现下降具有重要的地震短临预测意义。 研究认为 S 波分裂参数可以反映区域应力场的动态变化信息, 可以为安徽南部地区应力场研究与地震预测提供有用的信息。 相似文献
12.
Aftershocks induced by a large mainshock can cause additional damage to structures and infrastructure, hampering building reoccupation and restoration activities in a post‐disaster situation. To assess the nonlinear damage potential due to aftershocks, this study investigates the effects of aftershocks by using real as well as artificially generated mainshock–aftershock sequences. The real mainshock–aftershock sequences are constructed from the Pacific Earthquake Engineering Research Center—Next Generation Attenuation database for worldwide shallow crustal earthquakes; however, they are deemed to be incomplete because of missing records. To supplement incomplete real dataset, artificial sequences are generated on the basis of the generalized Omori's law, and a suitable aftershock record selection procedure is then devised to simulate time‐series data for mainshock–aftershock sequences. The results from nonlinear dynamic analysis of inelastic single‐degree‐of‐freedom systems using real and artificial sequences indicate that the incremental effects of aftershocks on peak ductility demand using the real sequences are relatively minor and that peak ductility demand estimates based on the generalized Omori's law are greater, particularly in the upper tail, than those for the real sequences. The results based on the generalized Omori's law also suggest that the aftershock effects based on the real sequences might underestimate the aftershock impact because of the incompleteness of the real dataset. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
13.
Temporal features of the aftershock activities following twelve moderate shallow earthquakes in Greece have been studied quantitatively, by making use of the modified Omori's formula and Akaike's Information Criterion (AIC).Although the earthquake sequences occurred in different seismotectonic regions in Greece, similar seismic patterns before the occurrence of large aftershocks have been observed. Aftershock activity shows an appreciable decrease from the level expected from the modified Omori formula before the occurrence of the large aftershock. Also in some cases, the aftershock activity recovers to a normal level or increases beyond it prior to the occurrence of the large aftershock, if the aftershock activity is monitored immediately after the occurrence of the main shock. In such case, the observed pattern may be useful in predicting a large aftershock. 相似文献
14.
Aftershocks of the 2011 Tohoku-Oki great earthquake have a wide range of focal depths and fault plane mechanisms. We constrain the focal depths and focal mechanisms of 69 aftershocks with M w > 5.4 by modeling the waveforms of teleseismic P and its trailing near-surface reflections pP and sP. We find that the “thrust events” are within 10 km from the plate interface. The dip angles of these thrust events increase with depth from ~5° to ~25°. The “non-thrust events” vary from 60 km above to 40 km below the plate interface. Normal and strike-slip events within the overriding plate point to redistribution of stress following the primary great earthquake; however, due to the spatially variable stress change in the Tohoku-Oki earthquake, an understanding of how the mainshock affected the stresses that led to the aftershocks requires accurate knowledge of the aftershock location. 相似文献
15.
1976年7月28日唐山MS7.8大地震对唐山及其周边地区造成了重大的人员伤亡和财产损失. 主震之后约15小时滦县又发生了MS7.1地震; 同年11月15日宁河也发生了MS6.9地震. 唐山MS7.8主震后的余震一直持续至今,使该区域至今保持了与主震前相比具有较高的地震活动性．如何估计余震的持续时间,并进一步将余震从主震目录中去除,一直是地震学中所关注的问题．该文通过对数线性回归和理论计算,从不同角度求取并讨论了1976年唐山MS7.8大地震的余震持续时间．结果表明,由对数线性回归计算得到的余震持续时间约为80 a．而基于Dieterich的余震触发理论所得到的余震持续时间则与区域剪应力变化率有关．区域剪应力变化率可有几种不同方法求得: ① 根据剪应力变化率和静态应力降Delta;tau;e及地震回复周期tr之间的关系求取应力变化率,该方法所得到的余震持续时间约为70——100 a;② Ziv和Rubin对Dieterich的方法进行了修正,给出了通过远场加载速率和断层宽度求取应力变化率, 该方法得到的余震持续时间约为80 a;③ 由背景场地震活动性求取远场剪应力速率, 可以得到该地区二维分布式的余震持续时间,此方法得到的研究区域内余震持续时间为130——160 a．综上,唐山地区余震持续时间约为70——140 a,据此, 该地区现今所发生的地震仍为MS7.8唐山地震所触发的余震． 相似文献
16.
In seismology according to Båth’s well-known law, the magnitude of the strongest aftershock is on average by unity lower than the magnitude of the main shock. At the same time, most of the strongest aftershocks typically occur within a few hours after the main shock. From the practical standpoint, this activity is quite naturally perceived as a direct continuation of the main earthquake. The subsequent strong aftershocks occur against the rarer background shocks, are less expected, and therefore constitute a separate hazard. The average difference in magnitudes between the main shock and the strongest aftershock that occurs a certain time after the main shock gradually increases. In this work, we consider the problem of estimating the magnitudes of the strongest future aftershock at the successive instants of time after the main shock without taking into account the information about the aftershocks that have already occurred before a given time. For these estimates, we construct the theoretical distributions whose shape proves to be independent of time, whereas the time dependence of the shift in the magnitude proves to be known a priori. The predetermination of these dependences at the moment of the strong earthquake gives us grounds to characterize the constructed theoretical model as Båth’s dynamic law. 相似文献
17.
综合利用川西流动地震台阵观测数据和震后应急地震观测台站的震相数据,采用双差地震定位方法对汶川地震的余震序列进行了精确重新定位,并对汶川地震的地震构造进行了深入研究.其结果显示,汶川地震序列从彭灌杂岩南缘开始破裂,主震及其余震破裂带长约350 km,在大部分区域宽约20~30 km,其宽度和空间形态沿破裂带显示了强烈的分段和非均匀特征.坚硬的彭灌杂岩对余震的非均匀性分布和汶川地震复杂的破裂过程起到了重要的控制作用.以松潘—甘孜地块中地壳低速层顶部为底边界,余震主要分布在4~24 km深度范围内的龙门山东缘上地壳高速层内.余震深度分布剖面清晰地显示了映秀—北川断裂和灌县—江油断裂以及汶川—茂汶断裂在20~22 km深度合并为剪切带的特征.小鱼洞到理县方向存在一条长度超过60 km的垂直于龙门山走向的余震分布条带,综合震源机制解和地震破裂过程的研究结果,我们推测,这是坚硬的彭灌杂岩体底部在长期应力积累作用下发生破裂的反映,并成为汶川地震释放出巨大能量的主要原因. 相似文献
18.
基于中国地震台网中心2013 MS7.0芦山地震余震数据我们首先确定了余震空间分布范围并根据G-R关系计算了主震后半小时内的完备震级Mc=3.5,并且得到了ML≥3.5和ML≥3.0的地震在2001年至芦山地震前的背景场地震发生率.通过Omori-Ustu经验定律和两种Dieterich模型对芦山地震余震发生率的拟合,我们发现阶梯型Dieterich模型只能模拟p=1的情况,从而造成了模拟曲线与观测数据的差别;前人研究表明震后滑移同样是产生余震的原因,如果假设余震序列由主震静态剪应力Δτ和震后滑移共同作用所产生,我们数值模拟得到的对数型Dieterich模型能够较好地推断余震发生率R随时间t增加而衰减的趋势,能够从物理机制上解释MS7.0芦山地震余震序列衰减指数大于1这一现象.通过对数型Dieterich模型的拟合并结合Andrews的方法,我们还得到MS7.0芦山地震Aσ约为0.155 MPa,ta约为8.4年,这一值与前人研究结果十分接近. 相似文献
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中强地震余震序列地震目录编目是否完备、 震源参数是否准确,直接影响余震序列特征分析、 震后趋势快速判断和强余震预测等研究结果的科学性和可靠性. 2013年7月22日甘肃岷县-漳县MS6.6地震余震序列目录中存在较多单台记录地震事件,地震观测报告仅给出其震级,而未给出震中位置. 由于余震波形间的相互交叠干扰,使得余震最大振幅的测量误差较大,造成地震观测报告给出的单台事件震级误差较大. 精确估计单台记录地震事件的震中和震级,能够补充完善现有地震目录,提高地震目录的完备性. 本文对单台记录地震事件震中和震级的估计不仅限于单个台站,而是通过分析区域台网中多个台站的波形记录实现. 首先以余震序列中震级较大、 波形记录信噪比较高的地震波形作为模板,使用波形互相关震相检测技术,检测单台记录的地震事件在多个台站的震相到时. 如果能在4个以上台站检测到震相,则利用测震台网常用的HYPOSAT方法估计其震中位置,并利用多个台站记录波形与模板地震的振幅比估计其震级. 之后计算主震发生后不同时间的最小完备性震级,并通过线性拟合得到最小完备性震级随时间变化的表达式,以分析此地震余震序列的目录完备性. 经过计算共得到253个单台记录地震事件的震级和其中177个事件的震中位置,其震中空间分布范围与余震序列中其它地震分布范围基本一致. 震级复测以及与人工拾取震相到时误差对比表明,该方法所得震相检测和震级估计结果具有较好的可靠性. 主震及最大余震发生后的短时间内,有较多数量单台事件的目录所给出的震级偏低,分析认为可能受主震与较大余震后续震相以及余震间相互干扰所致. 主震发生0.02—0.3天内,其余震序列最小完备性震级随时间的对数呈线性下降,在0.3天后最小完备性震级稳定在ML1.1左右. 相似文献
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地震序列类型能够直观地反映构造应力场环境、 地震构造及孕震环境介质的差异性。 主—余型地震多发生在相对均匀的介质环境, 而前—主—余型地震及震群型地震往往发生在复杂的构造环境。 2019年6月17日四川省宜宾市长宁县发生的6.0级地震余震活动总体呈NW向分布, 其南东段的余震呈相对单一的NW向条带状, 而北西段的余震活动呈现丛集的特征。 两段的地震序列类型也表现出明显的差异性, 南东段地震序列为主—余型, 序列衰减速度较快; 北西段地震序列为震群型, 序列初期衰减非常缓慢, 余震丰富。 此次6.0级地震序列发生在长宁—双河大背斜上, 该复式背斜主要由多个次级褶皱构造和不同走向的伴生断层组成, 结构复杂。 长宁6.0级地震序列的分段性特征表明, 该地震序列不是发生在单一的断裂构造上, 为多个构造级联破裂所导致的复合型地震序列。 此外, 序列北西段余震的深度逐渐变深, 可能预示着该区域受华蓥山断裂带活动的影响, 地震序列对华蓥山断裂带未来地震活动的影响应引起关注。 相似文献