大西洋中北部双频微地动特征

本文对大西洋中北部两侧五个地震台站2015年记录到的地震数据进行处理,计算噪声功率谱密度和概率密度函数,并通过极化分析对双频微地动不同周期的主导源区方位角分布进行了分析.研究结果显示:大西洋中北部台站双频微地动发生显著分裂,各台站的峰值周期各不同,且来自相同方向和不同方向的双频微地动都有可能产生双频微地动分裂;大西洋中...     

2011年日本MW9.0地震引发的海啸对地震背景噪声的影响

基于北美沿岸和内陆地震台站的连续地震波形记录,并结合沿岸台站附近布设的DART系统记录的海底压力数据以及预测潮汐数据,利用时频分析和极化分析方法对2011年3月11日日本东北部海域MW9.0大地震所激发的海啸对地震背景噪声所产生的影响予以深入分析.结果显示:海啸对高频噪声(1.3—1.5 Hz)以及短周期双频微地动噪声...     

2016年台风“尼伯特”激发微地动的频率特征分析

台风可以改变海面波浪状态并激发出微地动信号，该信号可以传播至陆地并被宽频带地震仪记录到。本研究以201601号台风"尼伯特"为例，利用短时傅里叶变换，分析了7月3日12时至7月9日0时台风期间中国台湾和日本114个宽频带地震仪垂向分量信号功率谱特征。分析结果发现，在7月5日至7月7日之间，当台风距离台站1500~2000km时，中国台湾、琉球群岛及屋久岛的33个地震台站的地振动信号功率谱密度值显著增强，7月5日前后，在0.4Hz频率左右出现功率谱密度值增强的现象，之后由高频转至低频，7月7日左右功率谱密度值增强频率变化至约0.2Hz。利用全球地震背景噪声能量辐射模型模拟KGM台站所在位置（128.22°E，26.76°N）的双频微地动功率谱，结果表明7月5日至7日0.2~0.4Hz功率谱密度值增强，频率由约0.4Hz变化至0.2Hz的现象为海岸线反射效应所致。     

汶川地震前地脉动信号的单台法研究

汶川地震前,我国及周边地区地震台站记录的地脉动信号显著增强,对这段时期内的地脉动信号进行频谱分析发现,它们的能量主要集中在0.20Hz附近.通过单台法对该频段信号进行定向,发现多个大陆和海岛台站记录的地脉动信号来源方向均指向我国东部海域,且方向变化与同期的威马逊台风路径保持很好的一致性.结合已有的地脉动信号强度随与台风...     

海岛地震台网自然因素对地脉动干扰分析

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。     

Statistical characteristics and stationarity properties of low-frequency seismic signals

Statistical properties of microseismic signals are studied in the frequency range 0.03–15 Hz at various points of the Earth near and far from sources of microseisms. It is found that various frequency ranges differ in the property of stationarity. The minimum interval of stationarity of microseisms in the range 0.12–1.1 Hz is estimated at 1–1.5 h. A conclusion is drawn that the measurement accuracy of the spectral density of microseisms cannot be improved above a certain limit by increasing the time of signal stacking.     

基于中国内陆大孔径地震台阵的Rayleigh面波噪声源分布特征研究

Rayleigh面波地震背景噪声成像技术已被成功运用到全球范围不同尺度的地球内部结构的研究中,并以背景噪声场是时空均匀分布为前提假设.然而真实的噪声源分布的时空非均匀性将导致经验格林函数提取存在偏差,最终影响噪声成像结果的精准性.近年来,噪声源分布特征研究逐步成为提高噪声成像精准度、深化地震背景噪声成像的关键问题.本文利用频率-波束域分析法对中国西北地区的一个大孔径台阵(WuTan Array,简称WTA)在2014全年的垂直分量连续记录做了聚束分析,研究了Rayleigh波噪声源分布特征.结果显示:WTA台阵成功探测到了10～20s周期范围的来自于全球不同方位的Rayleigh波噪声信号,其源区分布具有明显的季节变化特征:冬季集中分布在北大西洋方位,而夏季则转为印度洋方位噪声信号最强.此外,Rayleigh波噪声源区空间分布还表现出一定的频率依赖性,即在较低频段(0.0488～0.0635Hz)在北大西洋、北太平洋、印度洋及西太平洋四个方位均有分布;而在频率较高频段(0.0928～0.1025Hz)则集中分布于西太平洋方位.Rayleigh波噪声源时空分布特征和频率依赖性与海洋活动本身的季节性变化和频谱特征有关.并初步推测本文所观测到的Rayleigh波是由加剧的海浪运动直接作用于海岸、大陆架或海底而激发产生的第一类地脉动噪声信号.     

Comparison of microseisms of Cuban and Central European stations

Summary Oscillatory paths of microseisms and special characteristics of these paths at Central European and Cuban stations have been examined and compared. The question of the origin of the microseisms is also discussed.     

脉动和风暴的关系

一.脈動的原因 遠在十九世紀中葉,地震學者發現在地震圖上除了地震發生時的地震波以外,還有一種起伏不停的微小波動。這種微小的波動,除了因地震儀的性能及其四周環境改變所引起的突然震動外,還有一種比較有規律且帶有週期性的顫動。它的     

汶川大地震“震前扰动”存在“第三类脉动”吗？

采用国家地震台网数十台地震仪的观测资料研究了汶川大地震和昆仑山大地震的“震前扰动”现象,结果表明,“震前扰动”现象与强台风的影响密切相关,适用于英国海洋学家Higgins的海浪非线性干涉理论中的“第二类脉动”.然而,通过对信号时频特征的细致分析后发现：“震前扰动”信号存在着明显的“时频偏移”现象,不完全符合“第二类脉动”的特征.因此本文认为,汶川大地震的“震前扰动”除了包含“第二类脉动”信号外,还可能存在着“第三类脉动”,这对强震短临前兆的研究有重要意义.     

德令哈地震台测震干扰频谱特征及背景分析

通过3个台站地脉动频谱特征的对比,发现德令哈地震台地脉动记录6.5-7.5 Hz频段存在明显的高频干扰.根据2008年1月至2010年10月以来该高频干扰的频谱演化规律,对其产生背景来源做初步分析,在一定程度上解释了德令哈地震台P波记录个数减少的原因.     

On microseisms recorded near a coast

Summary In this paper two methods for analysing in real time (or on line) microseisms recorded near a coast, with the aim to deduce their fundamental periods and evolution, are presented. Firstly, the autocorrelation of microseisms as a random signal is derived, whereas the second method consisting in a frequential filtering is more extensively used. The application of these methods is also made for simultaneously recorded microseisms in Genoa and in Vesima-Arenzano (station placed just on shore-line). The results show that in Genoa the peak amplitude ratio between secondary and primary microseisms is varying in the range of 3–28, whereas in Vesima this ratio is about the unity. This behaviour is explained on account of the different breaking zones for the two stations.Istituto Geofisico e Geodetico, Università di Genova, 16100 Genoa, Italy. Contribution No. 249. — This work has been supported by the Consiglio Nazionale delle Ricerche (comitato Nazionale per le Scienze Fisiche), Roma.     

西北太平洋海岛地区地震背景噪声特征及海洋学解释

地震背景噪声特性及噪声源的分布研究逐渐成为深化背景噪声层析成像的关键问题.海岛地区由于特殊的地理位置,其背景噪声具有相对独特的特征.地脉动（约0.003~1 Hz）是地震背景噪声中能量最强的分量,其激发与特性被认为与海浪运动和固体地球之间的相互作用有关,但海岛地区地脉动特征与海洋波浪场之间的关系尚未被充分研究.本文利用西北太平洋海岛地震台站的连续记录数据、波浪浮标的实测数据以及WAVEWATCH-Ⅲ海浪模式的数值模拟结果,通过地震学和海洋学的交叉,分析海岛地区地脉动信号的时频特性及其与海洋波浪场之间的相关性,从海洋学角度对地脉动信号的特征及激发进行探讨与解释.结果表明,海岛地区地脉动信号相对于内陆地区更强,并具有明显且稳定的季节性变化特征：高频地脉动信号（0.12~0.32 Hz）在夏秋季节（5月-10月）相对较弱,而在冬春季节（11月-次年4月）相对较强,与北半球海洋活动季节性变化相一致.此外,海岛地区地脉动主要受周边海域波浪场影响,与周边海域波浪能功率密度及实测和数值模拟所得的有效波高均具有很好的互相关性.该研究结果同时表明可进一步发展利用地脉动观测数据反演海表波浪场的可能,为海洋科学研究中海表波浪场连续观测数据的获取提供地震学上的支持.     

A regional study of mantle velocity variations beneath eastern Australia and the southwestern Pacific using short-period recordings of P,S, PcP,ScP and ScS waves produced by Tongan deep earthquakes

Deep earthquakes located in the Tonga-Kermadec region produce exceptionally clear and sharp short-period P, S, PcP, ScP, and ScS phases which are recorded at many stations at distances of less than 60°. The data used in this study are produced by short-period stations located in oceanic-type regions (Fiji and New Caledonia), a mobile continental region (eastern Australia) and a shield region (central Australia). Differential travel-time residuals of the above phases at these stations are investigated to determine the contribution to the differential residuals from: (1) the upper part of the mantle (S-P residuals); (2) the core-to-station portion of the mantle (ScS-ScP residuals); and (3) the hypocenter-to core portion of the mantle (ScP-PcP residuals). The use of differential travel-time residuals considerably reduces near-station effects and effects due to inaccurate determination of the source parameters, and hence the results can be interpreted as due to variations along the propagation paths. The results show that (S-P) residuals from phases traveling along event-to-station paths are about 7 s smaller at the shield station than at the oceanic stations. This correlation with surface tectonic environments is equally strong for the (ScS-ScP) residuals, with the shield/oceanic station difference being about 4 s. Moreover, the data suggest that this correlation between differential residuals and surface tectonic environments is caused by variations in shear velocity within the upper part of the mantle. However, the data cannot uniquely resolve the required depth of these variations within the mantle. For example, if the shear velocity variations extend to a depth of 400 km beneath the recording stations, then the average shear velocity difference between shield- and oceanic-type environments is about 4%. However, if the variations extend only to a depth of 200 km, this difference is more than 8%.(ScP-PcP) and (ScS-PcS) residuals vary from about +1 to about +4 s at the different stations, apparently because of compressional velocity variations in the mantle along the Pc path. If the variation in compressional velocity within the mantle below a depth of about 600 km is about 10% and occurs near the source region, these results suggest that, in the vicinity of deep earthquake zones, variations in compressional velocity extend to a depth of about 1000 km. However, these results can equally be explained by a 1% variation in compressional velocity, evenly distributed along the entire Pc path. An estimate of Q determined from the observed predominant frequency of ScS waves, as recorded at the shield station, suggests that the average 〈Q_s〉 of the mantle beneath about 600 km is about 1050 at frequencies of about 1 Hz.     

腾冲炎山区微震类型与波谱分析

利用腾冲火山地区流动数字化地震台网的微震资料,对发生于火山区内及附近地区的２４个微小地震事件进行波谱分析。采用布龙模式计算震源参数。研究这些微震震源参数,显示位于火山区南部的热海和马鞍较高,主要以小震群、微破裂及汽爆等方式释放应力。通过对微地震记录事件的时域和频域分析,将腾冲火山地区微地震事件划分为四个类型,即包络型、汽爆型、高频型和震群型。     

Microseismic noise in the low frequency range (Periods of 1–300 min): Properties and possible prognostic features

The paper generalizes the experience accumulated in studies of microseismic noise in the period range from 1 to 300 min observed during time intervals preceding a few strong earthquakes. This frequency range is the least studied and occupies an intermediate position between low frequency seismology and investigations of slow geophysical processes. The range includes oscillations induced by atmospheric and oceanic processes and various modes of the Earth’s free oscillations excited by very strong earthquakes. The main attention in the paper is given to the background behavior of microseisms, which contains continuous present arrivals from near weak and far strong and moderate earthquakes. The paper focuses on the examination of synchronization effects arising in joint multivariate analysis of information from several stations with estimation of multifractal spectra of singularity and multidimensional spectral measures of coherent behavior of singularity spectral parameters. The problem of using the synchronization effects of microseismic background in the search for new precursors of strong earthquakes is discussed.     

Aswan telemetered seismograph network

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.     

2021年5月22日玛多MS 7.4地震地震动特征

为了研究2021年5月22日玛多M_S 7.4地震地震动特征,收集16个强震台的峰值加速度和其中9个台的强震波形数据,利用峰值加速度衰减及反应谱等分析玛多M_S 7.4地震强震动特征。结果表明,多数台站的PGA值都随震中距的增大而平稳下降,PGA的衰减特征与青藏区衰减关系间有较好的一致性;土层台与基岩台的加速度反应谱明显不同,震中距越小,短周期高频成分越多,衰减越快,震中距越大,长周期高频成分越少,衰减越慢;加速度反应谱的水平向与竖向比值曲线在4 s内呈现两峰一谷的现象,初步认为,距发震断层较近的野马滩1号大桥所受到的破坏及水泥路面的明显错断受水平向地震动作用的影响更大。     

地震勘探組合法之研究（一）

假定随机干扰是对位置平稳的随机变量,利用固定瞬间多道记录统计分析方法,讨论了组合地震法的统计效应及其效益,提出了在线性等距组合形式中组內间距选择以适应信杂比最大的条件,并讨论了选用组合形式和组內间距的方法。     

华东地区钻孔体应变对飑线天气过程响应的特征与机制

2018年3月4日华东地区爆发了一次强飑线天气过程,为揭示过境区域钻孔体应变对该飑线生命史期间的响应特征与机制,本文结合多普勒天气雷达和地面气象站数据,系统分析了南昌、黄山、湖州和岱山等4个钻孔体应变台的观测记录.结果表明:①飑线过境时的气压突变是引起体应变显著变化的主因,由此引起最大的体应变量为16.2×10-9;②...