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1.
When earthquake activity begins, it may be a foreshock sequence to a larger earthquake, a swarm, or a simple main-shock-aftershock sequence. This paper is concerned with the conditional probability that it will be foreshock activity of a later larger earthquake, depending on the occurrence pattern of some early events in the sequence. The earthquake catalogue of the Japan Meteorological Agency (1926-1993, MJ ≥4) is decomposed into a large number of clusters in time and space in order to compare statistical features of foreshocks with those of swarms and aftershocks. Using such a data set, Ogata, Utsu & Katsura (1995) revealed some discriminating features of foreshocks relative to the other types of clusters, for example the events' closer proximity in time and space, and a tendency towards chronologically increasing magnitudes, which encouraged us to construct models which forecast the probability of the earthquakes being foreshocks. Specifically, the probability is a function of the history of magnitude differences, spans between origin times and distances between epicentres within a cluster. For purposes of illustration, the models were fitted to the early part of the data (1926-1975) and the validity of the forecasting procedure was checked on data from the later period (1976-1993). Two procedures for evaluating the performance of the probability forecast are suggested. Furthermore, for the case where only a single event is available (i.e. either it is the first event in a cluster or an isolated event), we also forecast the probability of the event being a foreshock as a function of its geographic location. Then, the validity of the forecast is demonstrated in a similar manner. Finally, making use of the multi-element prediction formula, we show that the forecasting performance is enhanced by the joint use of the information in the location of the first event, and that in the subsequent interevent history in the cluster. 相似文献
2.
Smaller source earthquakes and improved measuring techniques allow the largest earthquakes in Iceland to be stress forecast (with hindsight) 总被引：3，自引：0，他引：3
Jing Wu Stuart Crampin Yuan Gao Ping Hao Theodora Volti Yun-Tai Chen 《Geophysical Journal International》2006,166(3):1293-1298
A group of three earthquakes in 2000 June in SW Iceland included the two largest earthquakes in Iceland in the past 30 yr. Previously, temporal changes in shear-wave splitting had not been recognized before these earthquakes as there were too few small earthquakes to provide adequate shear-wave data, and they were not stress forecast, even with hindsight. These large earthquakes were subject to a special investigation by the European Community funded PREPARED Project during which the seismic catalogue was extended to include smaller magnitude earthquakes. This more detailed data set, together with a semi-automatic programme for measuring the parameters of shear-wave splitting greatly increased the number of time-delay measurements.
The new measurements displayed the typical temporal variations before larger earthquakes as seen elsewhere: a long-term increase in time delays, interpreted as stress accumulation before the earthquake; and a decrease, interpreted as crack coalescence, immediately prior to the earthquake. The logarithms of the durations of both the implied accumulation of stress and the crack coalescence have the same self-similar relationships to earthquake magnitude as found elsewhere in Iceland. This means that, in principle, the time and magnitude of the larger earthquakes could have been stress forecast in real time had the smaller source earthquakes of the extended catalogue and the improved measuring procedures been available at the time. 相似文献
The new measurements displayed the typical temporal variations before larger earthquakes as seen elsewhere: a long-term increase in time delays, interpreted as stress accumulation before the earthquake; and a decrease, interpreted as crack coalescence, immediately prior to the earthquake. The logarithms of the durations of both the implied accumulation of stress and the crack coalescence have the same self-similar relationships to earthquake magnitude as found elsewhere in Iceland. This means that, in principle, the time and magnitude of the larger earthquakes could have been stress forecast in real time had the smaller source earthquakes of the extended catalogue and the improved measuring procedures been available at the time. 相似文献
3.
中国地震发生频率与烈度的空间分布 总被引：8，自引：1，他引：7
考虑不同区域地震记录具有时间长度不等的特点,对“震中分布分震级网格点密集值”算法进行改进,结合 GIS 的空间分析方法将地震目录中的点数据空间化为能反映地震发生频率的栅格数据;依据地震震级和烈度的关 系以及地震烈度在空间上的椭圆衰减模型,选择逼近和近似的计算手段,并结合空间插值方法得到中国地震烈度 分布的栅格图。从地震频率分布结果上看,大致以宁夏、甘肃、四川和云南为界,中国西部地区3 级以上的地震发生 频率要高于东部地区;从地震烈度分布结果看,中国甘肃、陕西、宁夏、山西、河北、四川、云南等位于地震带内的区 域在发生地震时产生的烈度较高。 相似文献
4.
采用ECMWF数值预报产品资料,首先用PP法和MOS方法建立溪洛渡水电站坝区三坪站气温预报逐步回归方程,寻找消空（漏）指标进行预报后处理,然后根据000～168时效的ECMWF数值预报产品资料制作未来24～144 h三坪站的最高、最低、平均气温预报。并研制出能自动运行的预报业务系统。2011年业务运行效果检验评估表明：系统预报效果较稳定,6 d平均、最高、最低气温平均预报准确率分别为70.8%、62.7%和76.0%,在水电气象预报服务中短期气温预报实时业务中有较好的指导作用。平均、最高、最低气温准确率随着预报时效的延长效果降低,平均气温和最低气温比最高气温的预报准确率高。预报方法对制作单站气温预报是可行的。 相似文献
5.
利用陕西省某一风电场区域内的观测资料,分析了该风电场的风速规律,并引入最优训练 期方案,研究利用线性回归方法建立风电功率预报模型的可行性。结果表明：该风电场区域,不同 高度的风速及其高度间的风速差异均表现出最大值出现在夜间,最小值出现在白天,从低层到高 层的风速日变化趋势一致的特征。一日中,风速与风电功率在 09:00 ~ 17:00 时段的相关系数明显
小于其它时段。按照风速是否大于 5 m·s-1 将训练期观测样本分为 2 组,可以明显改善风速与风电 功率的回归关系。以风机轮毂高度处的风速作为预报因子,并引入风电功率与风速之间相关系数 的日变化规律、以及不同风速量级下风速与风电功率之间回归关系的差异性,采用最优训练期方 案和一元线性回归方法建立的风电功率预报方程,具有预报误差小和最优训练期短的特点,满足 实际业务需求。 相似文献
6.
云南地震地质灾害与资源环境效应问题的初步研究 总被引：2，自引：1，他引：2
在对历史震害资料浅析的基础上，利用最近40年有现场调查的地震记录，分析了云南省各类地震地质灾害与资源环境破坏影响的一些特征，并结合云南地震时空活动特性，对云南有仪测地震资料近百年间的地震地质灾害与资源环境效应问题进行了反演，表明：（1）云南地区地震地质灾害与资源环境破坏影响具有群体分区特征。（2）云南地区存在时间进程上连续的中强地震活跃背景：地震对资源环境的作用影响具有强度为2级的高背景值。（3）云南资源环境地震破坏影响具有多侧面、长时效和渐微影响的特征。地震对资源环境的破坏，必将恶化人类生存条件，阻碍社会经济的长期与可持续发展。这是资源环境安全防震减灾所面临的新课题。 相似文献
7.
2008年汶川地震重灾区的泥石流 总被引：20，自引：1，他引：19
2008年,在"5·12"汶川地震后,随着降雨的发生,地震重灾区的中高山区较普遍地多次发生了泥石流灾害,尤其是对一些地震灾民安置点板房区造成了危害,累计造成人员伤亡(含失踪)达450余人,进一步加重了灾情.按照地震与泥石流暴发的时间顺序分类,区内的泥石流属后发型地震泥石流.其特征主要为:泥石流活动频率增高,暴发点多,规模大小不一,流体件质一般以粘性为主,密度值多在2.0-2.3t/m<'3>之间;泥石流的活动范嗣与降雨关系密切,活动范围还受地形因素控制,主要集中在龙门山等中高山区;泥石流危害形式有冲毁、淤埋、堵塞主河等多种形式.因此,在汶川地震重灾区这样的Ⅸ域选址恢复重建,实质上是在上程地质条件复杂的不稳定区内选择相对稳定的安全岛,町供选择的场地极为有限.故恢复重建居民点时应因地制宜,尤其是岷江等江河峡谷区等地的居民点重建,宜保持当地居民传统的分散、多点居住的特点,而不宜于搞成规模较大的集中成片的居民点.这样既有助于场址的安全,义可以避免大规模泥石流、滑坡、崩塌、山洪等山地火害发生时造成大量的人员伤亡.地震重灾区2008年的泥石流活动显示,龙门山及邻近的邛崃山等山区因汶川地震的影响,泥石流已进入强烈活动时期.其强烈活动时间,可能持续10～30 a,甚至更长.对此,要有足够的重视.在可能遭遇泥石流的区域开展的各种工程建设,一定要加强防范措施,防止泥石流危害. 相似文献
8.
Summary. The Lleyn Peninsular earthquake which occurred at 0656 on 1984 July 19 was recorded at three medium aperture seismological array stations located at teleseismic distances. From these recordings an estimate is made of the hypocentre, origin time, magnitude and fault-plane solution of the earthquake. The fault-plane solution was determined using the Pearce algorithm and indicates that the focal mechanism is predominantly strike-slip. The fault-plane solution was used to generate synthetic seismograms for comparison with the observed to confirm the nature of the source and in particular the depth of focus which was estimated to be 20.5 km. It is concluded that the determination of the earthquake parameters using only three teleseismic seismograms is in good agreement with the results obtained from an analysis of 45 local and regional seismological stations. 相似文献
9.
2017年7月陕西累计出现26 d日最高气温≥35℃的高温天气,其中14 d日最高气温突破40℃,7月7～14日和17～27日出现2次区域性持续高温天气。利用陕西99个国家站的最高气温逐时观测和ECMWF高分辨率模式的定时最高气温预报资料,检验ECMWF高分辨率模式对2017年7月陕西极端高温天气的预报能力和一元线性回归方法对气温预报的订正能力。结果表明:144 h之前模式较好地预报出了陕西2次区域性持续高温天气,但是高温日数的预报值在陕西大部分地区较观测值偏少,漏报了陕南大部分地区的高温日,与14:00～17:00时段最高气温的预报值在陕西大部分地区较观测值偏低,其中陕南地区的预报平均绝对误差明显大于其他地区有关。一元线性回归方法对168 h之前的最高气温预报为正订正效果,订正后陕西大部分地区最高气温的预报准确率上升,平均绝对误差减小,日最高气温≥35℃或≥40℃的高温预报较订正前更接近实况。 相似文献
10.
测氡在区域构造稳定性研究中的应用——以滇西北北部区域构造稳定性研究为例 总被引：4，自引：0，他引：4
研究表明，测氡在区域构造稳定性研究中是一种最经济，便利，省时又可靠的地球化学测试手段。在第四系覆盖区，它不仅可以确定覆盖层下断裂网络的空间格架，断层产状，断层的相对活动性，而且还能为地震预报提供重要信息。在滇西北北部区域构造稳定性研究中，运用测氡手段首次揭示北西向中甸－永胜断裂的存在，玉龙雪山的隆升机制和为工程区及其外围区域构造稳定性进行客观评价提供保证。 相似文献
11.
John Lovell Stuart Crampin Russ Evans S. Balamir Üçer 《Geophysical Journal International》1987,91(2):313-330
Summary. The third occupation (experiment TDP3) of recording sites above a persistent swarm of microearthquakes near the North Anatolian Fault, with a larger seismic network and over a longer period of time, confirms and refines previous observations with greater resolution. The greater resolution in earthquake locations has revealed marked clustering in time and space. Many, perhaps most, of the earthquakes belong to clusters, where successive earthquakes originate in a very small volume and have similar fault mechanisms. Such studies allow the progression of seismic activity of small earthquakes to be followed in some detail, and may reveal features which are hidden in larger and more complex earthquake sequences. 相似文献
12.
在候选预报因子的基础上,通过Pearson相关系数和重要度指数分别确定了主要预报因子及其滞后期,进而利用确定滞后期的预报因子建立基于随机森林的咸潮预报模型,并应用于磨刀门水道大涌口站的枯水期咸潮预报。结果发现：通过相关系数确定的主要预报因子与含氯度之间存在1~3 d不等的滞后期;考虑预报因子滞后作用的随机森林模型,其预报结果不仅能很好地满足咸潮预报的精度要求,而且明显优于未考虑预报因子滞后作用的随机森林模型,即考虑预报因子的滞后作用能显著提高模型的拟合效果。此外,与传统的马尔科夫链相比,随机森林模型的预报结果不仅精度更高,而且在中长期预报上更有优势。 相似文献
13.
地壳形变和地面温度异常是构造地震活动监测的两项重要指标,时间序列分析是提取地震活动异常信息的主要方法.该文以汶川地震为例,分析发现汶川震前位移、基线长度、应变分量时间序列出现显著的地壳形变动态异常,同震形变最为显著.分析地面温度增量时间序列,发现震前震中附近出现3次异常,持续时间为9～13 d,地面异常增温高达10°C,增温高值区主要沿龙门山断裂、鲜水河断裂、红河断裂展布,与活动断裂的空间分布具有很好的一致性.对同一像元应变与地面温度增量时间序列进行关联分析,发现地壳形变与地面温度异常特征具有一定的对应关系. 相似文献
14.
Local Modeling模式及其在月径流预测中的应用 总被引：5，自引：2，他引：5
Local Modeling方法是一种动力系统预测方法，将其应用于河西内陆区黑河干流出山口莺落峡水文站月平均流量的中长期预测预报，取得了较为理想的成果。预测试验的结果表明，该预测模型有较高计算精度，尤其适用于非主汛期各月的月平均流量的预测；对于主汛期6～9月的月平均流量的预测，在考虑前期来水与预见期内降水的影响后，亦可获到较为理想的预测结果。可以认为，该方法的预报精度达到了水文情报预报规范的要求，Local Modeling方法的应用，将为西北干旱地区河川径流的中长期预报提供了一个新的途径。 相似文献
15.
Likelihood analysis of earthquake catalogues 总被引：5，自引：0，他引：5
Y. Y. Kagan 《Geophysical Journal International》1991,106(1):135-148
We apply several classes of stochastic multidimensional models to statistical analysis of earthquake catalogues using likelihood methods. We investigate the importance of including different earthquake parameters in the model: epicentral coordinates, hypocentral depth, time limits for interearthquake interaction, and especially spatial distribution of earthquakes as well as spatial aftershock patterns. Results of this study combined with other investigations, suggest that most distributions controlling earthquake interaction have a fractal or scale-invariant form. Developed models are used for statistical analysis of several earthquake catalogues to evaluate parameters of earthquake occurrence. These parameters are shown to be similar for shallow earthquakes of different magnitude ranges and seismogenic regions, confirming self-similarity of the earthquake process. Whereas intermediate earthquakes seem to emulate the pattern of shallow earthquake occurrence, albeit at a much smaller aftershock rate, deep earthquakes differ significantly in their properties. Predictability of standard shallow earthquake catalogues has been analysed; we present evidence that for the best available catalogues the predictability is close to 10 bits per earthquake. Several synthetic earthquake catalogues have been created and processed through the likelihood inversion scheme. The results from likelihood analysis of these catalogues confirm our approach. 相似文献
16.
针对当前国内已有空气质量预报系统在数值预报计算模式更新方面存在的弊端,提出基于Ja va RMI的数值预报计算模式的构建方法,该计算模式具有易变性.通过分析两类传统方法在计算模式更新上存在的弊端,指出Java RMI的远端对象调用机制在实现方法上的优越性.阐述基于Java RMI的新方法的实现,展示如何在集成该处理模块的新系统中保证预报内容的准 确性、及时性及其良好的可扩展性. 相似文献
17.
掌握NMC和本地客观产品的气温预报能力,对提高宁夏城镇天气预报质量和全国排名有重要的意义。基于2009年1月～2014年12月T639和ECMWF两种模式产品及宁夏20个国家级观测站气温资料,采用资料按月和季划分的2种MOS方法,预报未来168 h最高、最低气温,运用宁夏现行的检验评估方法对2015年1月到2016年6月的预报效果进行检验,并与预报员（YBY）和中央气象台指导产品（NMC）对比,结果表明：MOS方法预报宁夏气温,整体预报效果优于NMC,资料按月划分的MOS预报效果优于资料按季划分,ECMOS月和T639MOS月是最高和最低气温的最优客观产品;最低气温预报中YBY优于T639MOS月,最高气温预报中ECMOS月优于YBY;两种最优客观预报产品一致的物理量为集中在中低层或地面的相当位温或假相当位温、温度、湿位涡、高度等,但各自还有一些起关键作用的入选因子影响最高、最低气温的预报。 相似文献
18.
面向地震应急准备的居民地遥感提取及量化分析 总被引：2，自引：1，他引：1
运用灰度共生矩阵、数学形态学等方法提取新疆新源地区高分一号2 m分辨率影像居民地信息,运用目视解译、影像叠加分析、缓冲区分析等方法,进行居民地量化分级,为地震应急准备提供数据支持。结果表明：研究区在地震烈度为Ⅷ度及以下区域,埋压主要集中在单层结构为主的建筑区;当地震烈度高于Ⅷ度且造成多层建筑大面积倒塌时,县城等人口密集区为首要救援区;在地震应急准备时,应对交通条件三等区和交通条件四等区重点关注,增加应急物资储备点,对山区居民地,应考虑道路毁坏情况,转换救援方式,做好应急预案。 相似文献
19.
Most seismic hazard estimations are based on the assumption of a Poisson process for earthquake occurrence, even though both observations and models indicate a departure of real seismic sequences from this simplistic assumption. Instrumental earthquake catalogues show earthquake clustering on regional scales while the elastic rebound theory predicts a periodic recurrence of characteristic earthquakes on longer timescales for individual events. Recent implementations of time-dependent hazard calculations in California and Japan are based on quasi-periodic recurrences of fault ruptures according to renewal models such as the Brownian Passage Time model. However, these renewal models neglect earthquake interactions and the dependence on the stressing history which might destroy any regularity of earthquake recurrences in reality. To explore this, we investigate the (coupled) stress release model, a stochastic version of the elastic rebound hypothesis. In particular, we are interested in the time-variability of the occurrence of large earthquakes and its sensitivity to the occurrence of Gutenberg–Richter type earthquake activity and fault interactions. Our results show that in general large earthquakes occur quasi-periodically in the model: the occurrence probability of large earthquakes is strongly decreased shortly after a strong event and becomes constant on longer timescales. Although possible stress-interaction between adjacent fault zones does not affect the recurrence time distributions in each zone significantly, it leads to a temporal clustering of events on larger regional scales. The non-random characteristics, especially the quasi-periodic behaviour of large earthquakes, are even more pronounced if stress changes due to small earthquakes are less important. The recurrence-time distribution for the largest events is characterized by a coefficient of variation from 0.6 to 0.84 depending on the relative importance of small earthquakes. 相似文献
20.
径流预测为流域水资源的合理开发利用与统筹配置提供依据。运用多元线性回归、主成分回归、BP神经网络及主成分分析和BP神经网络相结合的方法,对新疆呼图壁河流域石门水文站2009-2011年各月径流量进行预测,并采用相关系数、确定性系数及均方根误差对各模型预测精度进行比较。结果表明：（1）神经网络等智能算法具有高速寻优的能力,对短时间尺度的月径流量的预测结果较好;（2）主成分回归等常规算法能充分反映出某地区径流的年际的稳定性,对全年径流总量的模拟精度较高;（3）主成分分析和BP神经网络相结合的方法,提高了神经网络的收敛速度,同时降低了局部极值的影响,优于简单的BP神经网络,适用于呼图壁河月径流量预测。 相似文献