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1.
《地震地磁观测与研究》2016,(3)
热带气旋"威马逊"和"海鸥"活动期间,在热带气旋低气压和强降雨的特殊自然环境下,海南观测井水位大多呈抖动上升形态,而重力仪观测数据曲线粗糙,噪声变大。通过高通滤波及频谱分析,认为受热带气旋影响,水位变化与低气压相关性较好,热带气旋引起的水位抖动周期为1—10 min;重力观测曲线与热带气旋卓越周期及中心风速等因素有关。 相似文献
2.
2005年11月26日九江——瑞昌MＳ5.7地震发生前,震中及其周围地区的地磁基本场测量和相应的ldquo;2005.0中国地磁基本场曲面样条模型rdquo;显示,震中周围100 km范围内存在显著的ldquo;2005.0九江——瑞昌地磁基本场水平分量异常rdquo;. 而该异常在ldquo;1970.0中国地磁基本场曲面样条模型rdquo;中并不存在. 2005年12月在震中及其周围地区的21个测点上进行了地磁重复测量, 并建立了ldquo;局部修订2005.0中国地磁基本场曲面样条模型rdquo;. 该模型显示,震后ldquo;2005.0九江——瑞昌地磁基本场水平分量异常rdquo;明显减弱. 因此认为,ldquo;2005.0九江——瑞昌地磁基本场水平分量异常rdquo;是地震地磁前兆异常现象. 相似文献
3.
通过分析宁夏地区5口井水位记录的2013-2018年对中国大陆5级以上、全球7级以上地震的同震响应,计算了引起5口井水位同震响应地震震级与震中到观测井距离的阈值范围,即井水位记震范围及各观测井的记震特征,提出结合井水位记震范围与记震特征分析各井记震能力随时间变化的方法.结果表明,引起宁夏地区井水位同震响应的地震震级和井震距确实存在某个阈值范围关系,表示为地震能量密度,宁夏地区约为10-4 J·m-3;相较于以往判断井水位记震能力变化的方法,该方法提高了时间分辨率;当井水位记震能力发生变化时,井周边发生4.5以上地震的概率较高. 相似文献
4.
以华北地区1980——2010年资料为例,以单位边长的网格覆盖研究区,考察中小地震空间分布非空网格数的变化．网格尺度足够小则非空网格数趋于该时段的地震数,网格尺度足够大则非空网格数为1．实际资料显示,当空间网格尺寸大于0.5deg;之后,对结果稳定性的影响逐渐减弱．中小地震空间分布非空网格数的变化与ldquo;背景rdquo;地震活动的空间扩展（增强）或收缩（平静）有关．不同网格尺寸条件下的非空网格数有基本一致的变化趋势,可能间接反映了区域应力的短时扰动或起伏．小地震有更高的丛集特性,随着震级下限的提高,不同网格尺寸非空网格数之间差异逐渐变小．华北地区小震活动非空网格数的频次分布符合统计正态分布,因而给定置信概率、依据正态分布密度函数可计算非空网格数的ldquo;正常rdquo;分布范围,超出此范围的数据可视为异常．统计显示,就华北地区而言,中小地震非空网格数ldquo;平静rdquo;型异常的预测效率最低,ldquo;增强rdquo;型异常具有最高的报警对应率,而同时考虑ldquo;增强rdquo;及ldquo;平静rdquo;的异常判据则具有最高的预报评分．这也意味着,华北中强地震前以ldquo;增强rdquo;型的中小地震活动异常为主．研究结果还显示,小地震时空活动格局的改变与后续中强地震似乎具有更强的统计关联特性． 相似文献
5.
2008年5月9日,我国有13个地磁台（纳入国家地磁台网中心的台站）地磁垂直分量日变形态出现ldquo;双低点rdquo;异常．这些台站在空间上大致呈交汇的3个条带分布,其交汇处位于四川西部．异常出现3天后的5月12日,正好在四川西部的汶川发生了8.0级特大地震．地磁垂直分量日变ldquo;双低点rdquo;是客观存在的一种区域地磁异常现象．其成因可能是产生地磁静日变化Sq的外空涡旋电流体系发生变化,或可能是产生地磁静日变化的内源感应涡旋电流体系与外源涡旋电流体系产生数小时的滞后所引．地磁垂直分量日变ldquo;双低点rdquo;异常与地震的关系,可能是前者反映了地球深部地震孕育状态的加速变化. 相似文献
6.
分析了汶川MS8.0地震引起的甘肃ldquo;十五rdquo;数字化水位、水温同震响应特征.结果表明:① 响应灵敏性上,水位高于水温,井孔水温下段高于中段;② 响应起始时间上,不论是水位还是水温,均出现在Ｓ波达到之后;③ 同井并行观测的不同测项上,响应起始、结束或转折时间水位均早于水温;④ 响应起始时间与震中距的关系,当震中距相差比较大时,各测项起始时间随震中距的增大而延迟;⑤ 响应的曲线形态上,水位、水温大多表现为下降变化,并且同井观测的水位和水温在形态上很相似,具有很好的协调性特征,即同为上升或同为下降或同为振荡.通过对变化较稳定的响应过程进行曲线拟合分析,结果显示水位的响应曲线几乎均为3次曲线形态,而水温的响应曲线几乎均为对数形态. 相似文献
7.
汶川8．0级地震引起的中国大陆井水位同震响应特征分析 总被引：2，自引：0，他引：2
2008年5月12日汶川8．0级地震的发生不仅导致震中及附近地区井水位发生激烈的变化,而且还引起中国大陆大范围的同震水位变化。并且各台站记录到的同震水位变化具有不同的特征类型,从井水位变化的形态来看,井水位同震异常变化主要表现为三种不同的特征类型,即波动型、阶变型和持续缓变型变化。波动型同震水位变化是指,地震发生时井水位在地震波的影响下, 相似文献
8.
尼泊尔MS8.1地震引起中国大陆大量地震观测井水位和水温的同震响应. 从宏观结果看, 在54个同时存在水位和水温同震效应的观测井中, 有51口观测井的变化类型为水位上升-水温上升、 水位下降-水温下降、 水位振荡-水温上升或下降(以下降为主), 井水位与井水温同震效应表现出良好的相关性, 这可能与地下水动力学作用有关; 有3口观测井的水位变化与水温变化方向相反, 且水温变化均为震后效应. 另外, 有1口观测井水位无变化而水温同震效应明显. 这些不同类型的同震变化与井孔条件、 水温梯度、 传感器位置及水位埋深等多种因素有关. 从微观结果看, 井水位同震效应出现的时间及变化幅度与井水温同震效应出现的时间及变化幅度之间的关联性比较复杂, 这与井孔条件和温度梯度等因素有关. 相似文献
9.
以芦山、汶川地震震中为中心,选择了8个井点,对2个地震引起的井水位同震变化进行了比较,重点分析了3口同震变化反向的井点,即重庆的荣昌华江井、北碚柳荫井和四川的泸沽湖井。为使对比研究结果可靠,进一步收集了2011年3月11日日本9.0级地震、2012年4月11日苏门答腊北部海域8.6级地震引起的井水位同震变化资料。对汶川、芦山地震引起的同震体应变的计算结果显示：汶川地震时,荣昌华江井、北碚柳荫井和泸沽湖井水位同震变化与井点位置处的同震体应变一致,即位于同震体应变压缩区的井水位上升,位于体应变膨胀区的井水位下降;芦山地震时,3口井的水位同震变化与同震体应变不一致,表现出与日本、苏门答腊地震时相似的同震变化特征。 相似文献
10.
在文县地电场观测系统中实现了地震异常信号与干扰信号的分离技术．长年的观测实践证明,文县地电场观测点是一个很灵敏的ldquo;地震窗口rdquo;．研究表明,对于文县地电场观测点而言,震级、震中距、异常电信号幅度之间存在着线性关系;对带宽为0.003——0.003——30Hz的异常信号而言,震前异常的时间长短与异常开始至发震时刻的时间长短存在着密切关系,且与震中方位有关．这些关系为文县观测点预测未来地震时、空、强ldquo;三要素rdquo;提供了很有意义的经验公式,在给出昆仑山口西MS8.1地震预测意见中起到了良好的作用． 相似文献
11.
利用海南地震台网宽频带地震仪连续观测资料,分析不同自然环境下地脉动扰动信号,结果显示:在不同自然环境下,地震仪记录的地脉动扰动信号的形态、振幅、频率、扰动强度不同,其中登陆海岛的热带气旋引起的震颤信号频带窄、能量大、扰动强度较大,对地脉动干扰影响大,其次是天文潮期,远离海岛的热带气旋对地脉动干扰影响较小;不同路径、距离的热带气旋引起的震颤信号频率带一致,但扰动强度区别明显;不同自然环境对不同观测台站记录的地脉动信号均存在影响,只是程度稍有不同。 相似文献
12.
Tropical cyclones (termed hurricanes and typhoons in other regions), are extreme events associated with strong winds, torrential rain and storm surges (in coastal areas) and cause extensive damage as a result of strong winds and flooding (caused by either heavy rainfall or ocean storm surges) in the immediate area of impact. The eastern Indian Ocean, particularly in the northwest region of Australia, is impacted by up to 10 tropical cyclones during the cyclone season, although direct impact of cyclones along the west and southwest coastlines is rare. However, the sub-tidal frequency component of sea level records along the west and south coasts of Western Australia indicates lagged correspondence with the occurrence of tropical cyclones. It is demonstrated that the tropical cyclones generate a continental shelf wave which travels along the west and south coasts of Australia up to 3500 km with speeds of 450–500 km day−1 (5.2–5.8 ms−1) with maximum trough to crest wave height of 0.63 m, comparable with the mean daily tidal range in the region. The shelf wave is identified in the coastal sea level records, initially as a decrease in water level, 1–2 days after the passage of the cyclone and has a period of influence up to 10 days. Amplitude of the shelf wave was strongly affected by the path of the tropical cyclone, with cyclones travelling parallel to the west coast typically producing the most significant signal due to resonance and superposition with local forcing. Analysis of water levels from Port Hedland, Geraldton, Fremantle and Albany together with cyclone paths over a ten year period (1988–1998) indicated that the tropical cyclones paths may be classified into 6 different types based on the amplitude of the wave. 相似文献
13.
The tropical cyclones form over the oceanic regions where conventional meteorological observations are not available. This
contributes to a poor initial analysis of the cyclonic vortex and hence inadequate forecast. One way of overcoming the above
problem is to modify the initial analysis by replacing the weak and ill-defined vortex in the initial analysis with a synthetic
vortex having the correct size and intensity at the correct location. In this study we are investigating the effect of inclusion
of a synthetic vortex based on Rankine as well as on Holland wind profiles, using NCAR-AFWA bogussing scheme for the prediction
of four tropical cyclones, which formed over the Bay of Bengal during November 2002 and 2005, December 2005 and over the Arabian
Sea during May 2004, using the MM5 model. Two numerical experiments are designed in this study for each of the above four
cyclones. In the first experiment the model is integrated with a synthetic vortex based on Rankine wind profile while in the
second experiment we utilize the Holland wind profile. For the November 2002 cyclone, in both the experiments the model is
integrated from 10 November 2002 18 UTC to 12 November, 2002 12 UTC with the synthetic vortex inserted at the initial time.
The results of the study for the November 2002 cyclone show that the model simulation with the Holland vortex has produced
a stronger cyclone in terms of minimum sea-level pressure and maximum wind speed. Also, the results for the November 2002
cyclone with the Holland vortex showed a better longitudinal height section of the horizontal wind speed across the center
of the cyclone. The track error of the cyclone for the November 2002 cyclone is less in the model simulation with the Holland
vortex at the initial time and at 24 hours of forecast. The results for the November 2002 cyclone with the Rankine vortex
showed greater vertical wind speed as compared to the Holland vortex. However, for the November 2002 cyclone there were no
significant differences in the spatial distribution of precipitation for both the experiments. In order to provide an adequate
number of case studies for a good statistical sample, the present study is extended for three additional cyclones over the
Indian region. All four cyclones studied here show that the Holland vortex has produced a stronger cyclone in terms of the
minimum sea-level pressure and maximum wind speed. The Holland vortex showed a better vertical structure of wind speed in
the longitudinal height section at 24 hours of forecast for the November 2005 cyclone while the structure was better for the
Rankine vortex for the remaining two cyclones. There were no significant differences in the spatial distribution of precipitation
for the two experiments corresponding to all four cyclones. Some statistical results pertaining to all four cyclones are provided
such as the average track error as well as the average difference between the observed and the model minimum sea-level pressure
and the maximum wind speed. The statistical results corresponding to the average of all the four cyclones are at only a slight
variance with the results corresponding to the November 2002 cyclone. 相似文献
14.
Abstract Daily flow records, rainfall data and tropical cyclone maps during 1970–1998 are used to document the impact of tropical cyclones (TCs) on floods in the Rewa River system, Viti Levu, Fiji. Floods are large, brief, isolated events caused by TCs and non-TC tropical rainstorms. More floods are caused by tropical rainstorms than by TCs, but TC floods are larger. The log Pearson Type III distribution consistently provided the best fit to partial duration flood series and the widely-recommended generalized Pareto distribution performed very poorly, underscoring the need to test a variety of distributions for a particular geographic location. Tropical cyclones occur more often in Fiji during negative values of the Southern Oscillation Index (SOI) and all TCs that occurred during El Niño conditions caused floods. Peak flood discharges caused by TCs are inversely correlated with the SOI, reflecting possible links with tropical cyclone frequency and precipitation intensity. 相似文献
15.
全球地震台网(GSN)及中国地震台网(CENC)的地震观测数据分析表明:由北大西洋、北冰洋等海域进入北欧的强冷涡气旋(北欧风暴)能引发与其过程相关联的震动,其中由挪威海登陆斯堪的纳维亚半岛的强气旋风暴引发的震动波,几乎可以被整个欧亚大陆的地震仪观测到,该震动主要包含两个信号:一个主频为0.15~0.25 Hz(周期约4~7 s);而另一个是主频为0.08~0.12 Hz(周期8~12 s)的面波信号,它们分别来自不同的产生机理.不同海域和地区的风暴引发的震动信号存在差异,与气旋运动路径经过的地形地貌特征有关,气旋经过的浅海区域、海水深度、登陆地点的地形以及气旋的结构、观测点相对气旋的分布等因素决定了气旋在运动中激发有独特的震动信号.地震观测可以监测气旋在时间和空间的发展变化过程,有助于探索气旋运动过程中与地球表面的相互作用对气旋的影响. 相似文献
16.
Relationship between the Asian-Pacific oscillation and the tropical cyclone frequency in the western North Pacific 总被引：12，自引：1，他引：11
The relationship between the Asian-Pacific oscillation (APO) and the tropical cyclone frequency over the western North Pacific (WNP) in summer is preliminarily investigated through an analysis of ob- served data. The result has shown clearly that APO is significantly and positively correlated to the tropical cyclone frequency in the WNP. If APO is above (below) the normal in summer, more (less) tropical cyclones will tend to appear in the WNP. The present study also addresses the large-scale at- mospheric general circulation changes underlying the linkage between APO and the WNP tropical cy- clone frequency. It follows that a positive phase of summer APO is concurrent with weakened as well as northward and eastward located western Pacific subtropical high (WPSH), low-level convergence and high-level divergence, and reduced vertical zonal wind shear in the WNP, providing favorable envi- ronment for the tropical cyclone genesis, and thus more tropical cyclones will come into being, and vice versa. 相似文献
17.
本文利用美国海军台风警报中心（JTWC）提供的1945～2002年热带风暴路径资料统计分析了西北太平洋（NWP）和中国南海（SCS）风暴生成及登陆中国大陆热带风暴的时空演变特征.季节变化上，NWP风暴登陆主要集中于6～11月，SCS风暴影响主要集中在6～9月，但后者登陆总数比前者少.西北太平洋风暴在东南沿海(27°N，120°E)附近登陆的频次最高，在此以北随纬度急剧下降.年际变化时间尺度上，登陆大陆的风暴年总数与来自南海的年风暴数成正比.登陆我国的热带风暴年频数有明显的区域差异和显著的2～7年振荡.长期趋势上，两个海域的风暴年生成频数和登陆大陆的年风暴频数在58年中总体呈线性增长趋势，其中登陆频数增长趋势相对缓慢，但近几年登陆风暴数与生成风暴数都表现出减少的趋势.生成频数和登陆频数都呈现出年代际变化，其年代转换发生在1960、1970年和1990年前后. 相似文献
18.
Tropical cyclones affect storm-dominated sediment transport processes that characterise Holocene shelf deposits in many shelf environments. A summary of cyclone-associated deposits in the Great Barrier Reef published by Larcombe and Carter [2004. Cyclone pumping, sediment partitioning and the development of the Great Barrier Reef shelf system: a review. Quaternary Science Reviews 23, pp. 107–135 indicates a pervasive northwards orientation of deposits on the lee side of reefs and other obstacles. In this paper, we describe the geomorphology of reef talus deposits found in the Gulf of Carpentaria and Arafura Sea, Australia, that we attribute to tropical cyclones. The orientation of these deposits is also indicative of a consistent, along-coast transport pathway. The deposits are located on the leeward side of submerged coral reefs; they are up to 10 m in thickness, comprised of re-worked carbonate sand and gravel and radiocarbon dating indicates that they are of Holocene age. An explanation for the consistent along-coast cyclone transport pathway is presented based on previously published hydrodynamic modelling results. These models illustrate how currents generated by the passage of a cyclone are asymmetric in plan view, such that stronger flows are generated between the eye of the cyclone and the coast. The result of the passage of many cyclones over geologic timescales is a net along-coast sediment transport pathway located on the inner- to mid-shelf, possibly extending over the entire length of northern Australia's coastline. This process provides an explanation for the observed sediment transport patterns on modern tropical continental shelves, as well as a basis for the interpretation of ancient tropical shelf deposits. 相似文献
19.
An upwelling system exists in the coastal waters of the northern South China Sea (NSCS), a region that is frequently affected by tropical cyclones in summer. This study investigates the evolution of the NSCS monsoon-driven upwelling system and the effects of the Talim and Doksuri tropical cyclones on the system using in situ observational data obtained at three mooring stations, one land-based meteorological station, and concurrent satellite remote sensing data for the NSCS coastal waters from May to July 2012. The results show that the occurrence and evolution of the upwelling system were mainly controlled by the Asian southwest monsoon, while the eastward current also made important contributions to the upwelling intensity. A decrease in the bottom water temperature and shifts in the along-shore and cross-shore currents were direct evidence of the establishment, existence, and recovery of this upwelling. Tropical cyclones have significant impacts on hydrodynamics and can thus influence the evolution of the NSCS upwelling system by changing the local wind and current fields. Variations in water level and local current systems impeded the development of upwelling during tropical cyclones Talim and Doksuri in the study area, which have low-frequency fluctuations of approximately 2–10 days. These variations were the results of the coupled interactions between local wind fields, coastal trapped waves, and other factors. The hydrodynamic environment of the marine water (including coastal upwelling system) rapidly recovered to normal sea conditions after each cyclone passed due to the relatively short duration of the impact of a tropical cyclone on the dynamic environment of the waters. 相似文献
20.
The characteristics of seismic water level fluctuations of the two Sumatra-Andaman strong earthquakes with magnitude 8.7 and 8.5 on December 26,2004 and March 29, 2005 recorded at Jiaji well, Qionghai, Hainan were analyzed, the features of the infrequent ＂step＂ changes of well water level after the two earthquakes were also analyzed and the mechanism of the ＂step change＂ of well water level was discussed. Then the high-sample-rate digital observation data of seismically-induced water level fluctuations of the Sumatra-Andaman strong earthquakes with magnitude 8.7 and 8.5 recorded at Nanbin well, Sanya and Tanniu well, Wenchang were analyzed. The results suggest that the dominant period of the seismic well water level fluctuation in all three wells was comparatively accordant, the amplitudes of seismic water level fluctuation of the same earthquake in different wells were clearly different, the time duration of seismic water level fluctuations of different earthquakes at the same well was also clearly different. 相似文献