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1.
对泰安地震台记录的2010年9月4日新西兰地震波形,进行震相、震源深度等地震参数辨析和分析,以具有代表性的2009年7月15日新西兰南岛西海岸远海地震波形和2010年4月5日墨西哥地震波形分析为辅,提出震中距大于83°、小于105°的类新西兰地震分析方法.根据两个辅震的波形特性,结合中国地震台网中心定位结果,对震级误差... 相似文献
2.
P.M. McGregor 《Physics of the Earth and Planetary Interiors》1979,18(2):105-113
The Bureau of Mineral Resources, Geology and Geophysics provides seismological services which complement those provided by several other agencies.The services comprise the operation of 20 seismograph stations in continental Australia, and the operation of regional data centres for earthquakes and strong earth-motion data. The ambit of the data centres includes BMR stations in Antarctica and Papua New Guinea, and foreign stations in Papua New Guinea and the Solomon Islands. Most of the data are lodged at World Data Centres, and the remainder are available from the BMR national centre.The combined Australian network has provided data at a regional level only for about the last twenty years. These have however, been sufficient to show that although seismicity is low it is not insignificant, and that there are several areas where damaging earthquakes can be expected to recur at 50-year intervals; about 500 Australian earthquakes are located annually.Complete national location capability does not extend below Richter magnitude 4, and it is unlikely that significant improvements can be expected in the near future. In most of the areas where earthquake risk is important from a civil standpoint the detection capability is about magnitude 3. For the other more remote areas advanced techniques based on unattended seismometers and satellite telemetry will probably be needed to attain the same capability. 相似文献
3.
倾斜扰动与短临地震预报 总被引：10，自引：0，他引：10
依据丽江、云龙、云县、保山、通海等台水平摆倾斜仪原始记录图资料，发现震前均存在倾斜扰动。从震源机制，岩石力学角度出发，认为倾斜扰动其本质就是微破裂、粘滑现象，是大震前有效的前兆，这些震兆信息被不同于地震仪固有频率特性的水平摆倾斜仪记录到。把这些特征同震源区岩体紧密联系起来，探讨震前孕震体变化过程与机理和短临地震预报的有效途径。 相似文献
4.
Raoul Island, the largest of the Kermadec Group, is about 8 km across and is situated about 1100 km north-east of Auckland, New Zealand. An eruption of steam and mud occurred on the island on 1964 November 21 (local date); this was preceded by an earthquake swarm which started on 10 November. Records made with the Willmore seismograph at the Meteorological Station on the north coast of the island show that within four hours of the start of the swarm, the frequency of shocks had risen to a peak of more than 80 an hour. Most shocks had sharp beginnings with S-P intervals of 1 to 2 seconds. Tremor was noticeable on 11 November and increased until by 12 November it was continuous, masking all but the largest of the discrete shocks. The level of tremor and the number of recorded shocks then decreased, until by the time the largest earthquake occurred on November 14, only 30 to 40 shocks were being recorded per hour. The largest earthquake was assigned a magnitude of 5.7 from recordings made in New Zealand, and was felt on Raoul Island at intensity 7 on the Modified Mercalli scale. Further shocks and tremor were recorded, and on 15 November the tremor was particularly active for several hours. On 21 November, an eruption occurred, throwing steam, mud, and rocks to an estimated height of 800 m from a crater on the edge of Green Lake, about 2 km from the Meteorological Station. During the eruption the seismograph recorded a peak vibration 30 to 40 times the amplitude of the normal background level. By two hours after the eruption, the level of vibration had stabilised at double that before the eruption. The island was evacuated from 23 November until 6 December, during which time the seismograph was inoperative. From 6 December to 11 December three portable seismographs were recording in addition to the permanent station. By this time the frequency of recorded shocks had dropped to about two per hour. The earthquakes were located in the vicinity of Denham Bay, some kilometres to the west of the main crater. Volcanic activity has been observed previously in Denham Bay, and it is thought that the Bay may be a former crater. 相似文献
5.
被普遍记录的最小震级是表征地震检测能力的重要标志。利用地震频度—震级关系统计了地震观测系统的检测率。引进了相应于70．7％检测率的系统震级下限参量mr以定量表征地震检测能力。以1970-2005年36年来的地震观测目录为基础数据,客观统计了中国大陆地区地震台网的检测水平。 相似文献
6.
以2015年河北昌黎ML4.5地震中测震、强震及烈度仪台站记录到的事件波形为研究对象,通过对比分析挑选的两组观测台站的记录波形以及不同台站的噪声记录特征,获得了烈度仪台站观测记录能力及特点的认识.结果表明:烈度仪台站产出的记录在部分频段 (1—10 Hz) 与传统强震台站、测震台站均有较好的一致性,但在中长周期部分存在较大差异;在相同观测频带 (0.1—10 Hz) 下,由烈度仪台站记录积分得到的速度时程、位移时程也与强震台站、测震台站的观测结果具有良好的相关性,说明烈度仪台站产出的加速度记录具有一定的可积分性;烈度仪台站记录的噪声水平远超出强震台站和测震台站,基本为仪器自噪声,不包含天然地脉动成分.此外,由于本研究所用的烈度仪采用了16位的A/D转换器,对震相到时的精确拾取产生了不利影响.综上,本文认为烈度仪台站较适用于中强地震的近场观测. 相似文献
7.
库尔勒数字地震台台基噪声分析 总被引：1，自引：0，他引：1
选取库尔勒地震台FBS—3数字地震仪不同时段的无震记录资料，运用傅里叶变换对其台基噪声进行频谱分析，并计算台基的平均噪声水平及仪器的实际动态范围。库尔勒地震台数字地震仪台基噪声主要来自随机干扰，噪声频段相对稳定，噪声幅度随时段有所变化。观测系统实际动态范围符合数字地震仪架设的要求。 相似文献
8.
本文再给出1976年7月唐山地震以外的我国10次地震前地电阻率(ρx)变化的震例,其中包括 M≥6的强震震例5次.每次地震前震中附近均有二个以上的台记录到(ρx)值同步变化.部分震例还对比给出地电阻率台附近测地基线的资料.发现不少地震前震中区浅层的(ρx)值有下降现象,这与唐山震例[1,2]相似,但也记录到(ρx)值上升或反复升降的例子.目的只是为了提供和积累更多的现象.因为一次大地震前,在震中附近设有地电阻率观测台而有记录的机会,就全世界来说尚是极少的.尽管这种变化仅局限于地表以下的浅层. 相似文献
9.
Egypt is recognized as a moderate seismicity region where earthquakes are distributed within several active regions. Owing
to sparse distribution of both seismicity and seismic stations, mostly moderate-size Egyptian earthquakes were recorded by
regional stations. One of such cases is the moderate-size earthquakes of moment magnitudes greater than 4.0 which struck the
Western Desert of Egypt in 1998 and 1999. These events are the first instrumentally recorded earthquakes occurring in the
area. In the present study, the source mechanism for these earthquakes was estimated using the waveform data recorded from
one of the very broadband MedNet seismograph stations and polarities from the national short-period seismographs. An iterative
technique was applied to find the best-fit double-couple mechanism by a grid search over strike, dip and rake. Regional synthetic
seismograms were calculated by using f–k integration in the frequency range of 0.03–0.1 Hz. A crustal structure fitted to surface wave dispersion curves was used
to compute Green’s function. Focal depths were determined through the grid search method for a range of source depths. Our
results show a normal faulting mechanism with minor strike-slip component. The NNW trend has been chosen as a preferred rupture
plane in consistence with surface and subsurface faults and microearthquake seismicity in the epicenteral area as well. 相似文献
10.
David J. Dowrick 《地震工程与结构动力学》1991,20(6):577-596
The surface-wave magnitudes of a selection of New Zealand earthquakes have been determined on a consistent basis using the ‘Prague formula’ and station corrections. The earthquakes range in magnitude from about 5 to 7.8, covering the instrumental period 1901–1988. Magnitudes for many of the earlier events had not been properly determined previously; and some significant discrepancies from the traditional magnitudes were found. The use of European station data (160° < D < 175°) is important to New Zealand because of its geographical isolation. These distant data were found to give consistently slightly higher Ms than closer stations, but could be used without bias through the station correction procedure. The relationship between Ms and ML was found for 31 ‘shallow’ New Zealand events and much of the scatter was explained as a function of depth. Significant differences in Ms/ML expressions from Europe and California were also found. The limited New Zealand data for Mw and M0 related well to Californian and global relationships with Ms. 相似文献
11.
William Power Laura Wallace Xiaoming Wang Martin Reyners 《Pure and Applied Geophysics》2012,169(1-2):1-36
We assess the tsunami hazard posed to New Zealand by the Kermadec and southern New Hebrides subduction margins. Neither of these subduction zones has produced tsunami large enough to cause significant damage in New Zealand over the past 150?years of well-recorded history. However, as this time frame is short compared to the recurrence interval for major tsunamigenic earthquakes on many of the Earth’s subduction zones, it should not be assumed that what has been observed so far is representative of the long term. For each of these two subduction zones we present plate kinematic and fault-locking results from block modelling of earthquake slip vector data and GPS velocities. The results are used to estimate the current rates of strain accumulation on the plate interfaces where large tsunamigenic earthquakes typically occur. We also review data on the larger historical earthquakes that have occurred on these margins, as well as the Global CMT catalogue of events since 1976. Using this information we have developed a set of scenarios for large earthquakes which have been used as initial conditions for the COMCOT tsunami code to estimate the subsequent tsunami propagation in the southwest Pacific, and from these the potential impact on New Zealand has been evaluated. Our results demonstrate that there is a significant threat posed to the Northland and Coromandel regions of New Zealand should a large earthquake (M w ?8.5) occur on the southern or middle regions of the Kermadec Trench, and that a similarly large earthquake on the southern New Hebrides Trench has the potential to strongly impact on the far northern parts of New Zealand close to the southern end of the submarine Three Kings Ridge. We propose logic trees for the magnitude–frequency parameters of large earthquakes originating on each trench, which are intended to form the basis for future probabilistic studies. 相似文献
12.
The arrival time difference for the AB branch of PKP from deep Tonga earthquakes is constant over years with a standard deviation
of ±0.05 seconds at seismographs located 10 to 50 km from each other. If published travel time curves are used to calculate
the relative residuals of PKP the standard deviation from the constant mean is improved by approximately 0.01 seconds for
AB branch data. For the BC branch, standard deviations of relative travel times of ±0.06 seconds are reduced to less than
±0.05 seconds by calculating relative residuals. We conclude that changes of crustal transit time forP-waves could be resolved, based on careful PKP arrival time measurement at two or more neighboring stations if the changes
exceed 0.05 sec and last for more than one year. The conditions for achieving this result are that PKP from Tonga earthquakes
is clearly recorded, and that time-keeping is accurate. The data on which these conclusions are based were obtained from the
Graefenberg seismograph array, which is located in West Gemany and consists of 13 stations separated by distances of 10 km
to 100 km. We propose that relative arrival times of PKP from Tonga could be used in the Mediterranean - Middle East area
to search for precursory travel time changes before large earthquakes. 相似文献
13.
2002年8月20日长白山天池火山小震震群研究 总被引：17，自引：2，他引：17
2002年7～9月，采用15台宽频带流动地震仪在长白山天池火山区进行了近3个月的地震观测，记录到大量发生在天池火山附近的地震和多次小震群。对2002年8月20日的小震群进行了分析，结果表明这些地震发生在长白山天池内的西南部，震源深度距离天池水面一般小于4km深，震群的震中位置呈北西向线性分布。地震记录的频谱分析表明，该震群为典型的火山构造类型地震。在观测中发现HSZ和DZD台的地震记录低频成份丰富，这可能与台站附近的局部介质变化或低速的断层带有关。我们认为震群可能是由火山深部活动诱发的局部断裂活动所引起。 相似文献
14.
张北地震前小震活动和余震序列精确定位及主震破裂方向的讨论 总被引：3，自引：0，他引：3
1970年至1998年1月10日张北地震前,沿NWW向发生2级以上地震24次,其分布相对集中,呈条带状。对华北台网所记上述地震的到时数据全部重新查图核对,并补充了内蒙古台网5个台的数据以改善用于定位的台站分布,并采用主地震定位法重新定位,除一个地震外,其余地震更加集中,形成一小震条带。1998年2月中国地震局地球物理勘探中心在张北震区架设10台短周期数字化地震仪,记录了大量微震。作者采用P波和S波到时差重新进行了震源定位,得到184次微震的定位结果,连同1998年1～2月张北震区3级以上地震事件定位结果一起勾画出6．2级地震的震源破裂带。由张北地震震中向SEE向延伸存在由强震构成的张家口渤海地震带。根据精确定位结果,结合修订后主震的震源机制、宏观烈度分布和层析成像资料,讨论了张北地震和小尺度地震带(震源破裂带)、震前的中等尺度小震条带以及大尺度的张家口-渤海强震带的关系。 相似文献
15.
D.W. Simpson R.M. Kebeasy C. Nicholson M. Maamoun R.N.H. Albert E.M. Ibrahim A. Megahed A. Gharib A. Hussain 《Journal of Geodynamics》1987,7(3-4)
A telemetered network of 8 short-period seismograph stations was installed at Aswan Reservoir in July 1982 to monitor induced seismicity near the site of a magnitude 5
earthquake which occurred in November 1981. A continuous monitor of the seismicity is provided by pen and ink recording of 4 stations. An event detector is used to identify events of interest, for which all of the stations are recorded on magnetic tape. Approximate displacement magnifications are 40, 000 at 1 hz with a maximum of 500, 000 at 20 hz. 相似文献
16.
利用国家测震台网数据备份中心时间跨度超过7年的连续波形资料, 设定至少三个台站记录的垂直分量波形互相关系数大于0.8的地震对为一组重复地震, 通过波形互相关分析, 识别出龙门山断裂带周缘波形相关意义上的“重复地震”2790次, 构成2907组重复地震。 沿用Schaff和Richards的研究结果, 假定“重复地震”间距很小(小于1 km), 地震目录记录的重复地震对位置之差主要为地震台网的定位误差所致, 基于此误差给出了龙门山断裂带周缘地震台网的定位精度估计: 台网的水平定位精度较高, 水平定位误差约为2.8 km(2倍标准差), 且西南段台网的水平定位精度优于中北段; 垂直定位精度较差, 垂直定位误差约为10 km(2倍标准差), 现有地震定位方法对震源深度的测定有待改善。 相似文献
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根据欧亚大陆及西太平洋地区102个数字化台站记录的近万次地震事件的长周期垂直向瑞雷波资料,利用时频分析方法测量并筛选后共得到11213条质量较高的基阶瑞雷波群速度频散资料.纯路径频散的反演中同时计算方位各向异性,反演获得了欧亚大陆及西太平洋边缘海地区(10°E—150°E,10°S—80°N)8—200s共28个周期的瑞雷波群速度及各向异性空间分布图象.瑞雷波高分辨率层析成像表明,30—60s周期,以青藏高原为中心呈极低速分布;100—120s周期,速度差异幅度较大,在东亚东部及西太平洋边缘海,自北向南显示出一条宽2500—4000km,长约8000km的巨型低速异常带.相对海洋来说,欧亚大陆各向异性强度较弱且快波方向较复杂.由于受到印度板块与欧亚板块的碰撞,中国大陆西部的各向异性强度明显大于东部. 相似文献
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震源机制解,即对地震矩张量的推断,对于地震研究具有至关重要的意义.应变地震观测是张量观测,与摆式地震仪的位移矢量观测不同,可以为地震研究提供新的数据源.本文讨论用应变地震观测求解震源矩张量的基本原理.在距离震源足够远的地方,地震波可以看成平面波,其性质决定于震源矩张量.假设平面地震波的应变张量可以由震源矩张量通过坐标变换计算得到,就可以通过观测应变地震波求解震源机制.这个假设至少对于双力偶震源机制是成立的.由此可以证明,在理想的无限介质中,只要有两个以上不同地点的应变地震波观测,就可以解出震源矩张量.这为解决震源机制问题提供了新的方法.目前的地震矩张量求解方法需要两方面的条件:或者需要很多观测点(例如体波反演),或者需要长周期地震波资料(例如面波反演).这些方法只适用于分析比较大的地震.对于小震,因为通常其震中周围不会有足够多的摆式地震仪观测点观测到其地震波,而地震波周期又短,难以利用传统方法给出可靠的震源机制解,所以只需少数观测点就能求解震源矩张量的新方法特别有意义.用应变地震观测求解震源机制,可以给出更为精确的结果. 相似文献