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1.
Automatic pickings in earthquake real-time monitoring systems often contain noise bursts and/or phases of different event(s)
occurring almost simultaneously. Typically, a locator uses these picks as P and S waves arrival times coming from a single
event and, therefore, should be complemented by a distinctive phase association logic. The method we propose manages to automatically
associate data related to different events and eliminates the influence of spoiled data from single events. The method is
based on “network beamforming”, a robust and stable algorithm, which utilizes a hypocenter grid search for the stack maximum
of a set of complex exponents applied to the P phase readings. The algorithm separates the residual outliers and then uses
them for location. If successful, a hypocenter is established for the interfering event. The solutions obtained are overall
robust and independent from the estimate of origin times. The preliminary epicenter for the grid search is provided by the
intersection of perpendicular bisectors in the modified “arrival order algorithm” or by the modified “Tnow” algorithm, which uses non-arrival information. We applied this method to automatic first arrival phase readings of 915 events
registered by the Hi-net Japan seismic network and our results are statistically promising. Here, we present two interesting
and complicated examples. 相似文献
2.
The accuracy of automatic procedures for locating earthquakes is influenced by several factors such as errors in picking seismic phases, network geometry, modeling errors and velocity model uncertainties. The main purpose of this work is to improve the performances of the automatic procedure employed for the “quasi-real-time” location of seismic events in North Western Italy by developing a procedure based on a waveform similarity analysis and by using only one seismic station.To detect “earthquake families” a cross-correlation technique was applied to a data set of seismic waveforms recorded in the period 1985-2002, in a small test area (1600 km2) located in the South Western Alps (Italy). Normalized cross-correlation matrices were calculated using about 2700 seismic events, selected on the basis of the signal to noise ratio, manually picked and located by using the Hypoellipse code. The waveform similarity analysis, based on the bridging technique, allowed grouping about 65% of the selected events into 80 earthquake families (multiplets) located inside the area considered. For each earthquake family a master event is selected, manually re-picked and re-located by using Hypoellipse code. Having chosen a reference station (STV) on the basis of the completeness of the available data set, an automatic procedure has been developed with the aim of cross-correlating new seismic recordings (automatically picked) to the waveforms of the events belonging to the detected families. If the new event is proved to belong to a family (on the basis of the cross-correlation values), its hypocenter co-ordinates are defined by the location of the master event of the associated family. The performance of the proposed procedure is tested and demonstrated using a data set of 104 selected earthquakes recorded in the period January 2003-June 2004 and located in the test area. The automatic procedure is able to locate, associating events with the multiplets detected by the waveform similarity analysis, about 50% of the test events, almost independently of the accuracy of the automatic phase picker and without the biasing of the network geometry and of the velocity model uncertainties. 相似文献
3.
准确拾取P、S波震相到时是深入开展地震波研究工作的基础,本文改进了自动拾取参数优化函数算法和质量评估方案,引入了拾取到时优化方案,使用基于参数优化的频带-带宽拾取算法、AICD拾取算法和峰度拾取算法对腾冲地区7个宽频带地震台站记录的地震资料开展了地震P、S波到时自动拾取,对拾取结果进行了优化和质量判定.结果表明：经参数优化、拾取优化后,采用3种方法自动拾取的P、S波到时与人工拾取到时的时差在0.1 s内的记录占比分别达到74.66%、70.98%.这些参数值均优于算法改进前的同类参数,证明了优化方法的可靠性. 相似文献
4.
将深度学习到时拾取、震相关联技术与传统定位方法联系起来,构建一套连续波形自动化处理与地震目录自动构建流程,对于高效充分利用地震资料,提升微震检测能力具有十分重要的意义.我们应用最新发展的迁移学习震相识别技术、震相自动关联技术,对长宁M S6.0地震震中附近21个台站震前半个月(6月1日—6月17日)的连续记录波形进行P、S震相识别、震相自动关联和初步定位,并应用传统绝对定位和相对定位技术得到了长宁地震震前微震活动的绝对和相对定位目录.其中绝对定位目录能在较小的误差范围匹配85%的人工处理目录,其发震时刻平均误差为0.36±0.07 s,震级平均误差为0.15±0.024级,水平定位平均误差为1.45±0.028 km,其识别的1.0级以下微震数目是人工的8倍以上,将长宁地震震前微震目录的检测下限提升至M L-1左右,证明了基于深度学习到时识取和REAL(Rapid Earthquake Association and Location,快速震相关联和定位技术)震相自动关联来构建微震目录具有较好的实用性.我们的自动地震目录揭示了长宁M S6.0主震所发生的区域震前异常频繁的微震活动,以及与区域内盐矿注水井的关联性,更好地描绘了这些微震活动的时空演化特征,其空间活动性分布特征与长宁M S6.0余震序列的分布一致. 相似文献
5.
In this paper, based on the previous study of practical use of seismic regime windows and seismic regime belts, the problem
of establishing a “seismic regime network” consisting of “windows” and “belts” is further posed and discussed according to
the observed fact that many “windows” and “belts” make responses to one earthquake. For the convenience of usage, the “seismic
regime network” is divided into two classes, the first class and the second one. The former can be used in tendency prediction
for long-term seismic activity in a large area, the latter used in short-term prediction in a small area. In this paper, after
briefly discussing the physical significance of “seismic regime network”, it is pointed out that this simple and easily used
method can be used to observe and extract seismic precursory information from a large area before a great earthquake, thus
it can provide a reliable basis for the analysis and judgement of seismic regime tendency in time and space. No doult, this
method is of certain practical significance.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 161–169, 1991.
The English version of this paper is improved by Prof. Shaoxie Xu. 相似文献
6.
针对微震事件易受噪声干扰等特点,本文将STA/LTA方法和基于方差的AIC方法（var-AIC）相结合,在震相到时初步拾取的基础上,使用台站的德洛内（Delaunay）三角剖分及台站间最大走时差约束来减少噪声干扰的影响. 利用到时进行地震定位之后,根据台站预测到时,在设定的时间窗内对地震震相进行更精细的分析. 特别是针对微震事件信噪比低的特点,设计了基于偏振分析的拾取函数,根据窗内STA/LTA方法和var-AIC方法的拾取结果自动选择合适的值作为震相到时. 最后,对西昌流动地震台阵2013年304个单事件波形数据的分析处理和检验结果表明,本文方法较传统方法具有更高的地震事件检测能力和更高的震相拾取精度. 相似文献
7.
Luan-Sheng Su 《地震学报(英文版)》1995,8(1):51-56
Based on the observations of many years, it has been found that “small earthquake modulation windows” exist in the situation
of some special geological structures, which respond sensitively to the variations of regional stress fields and the activities
of earthquake swarms greater than moderate strong magnitude, and can supply some precursory information. More than two “small
earthquake modulation windows” can also provide a general orientation of the first main earthquake of a earthquake cluster.
Compared with “seismic window” based on frequency it is no doubt that the “modulation-window” has an unique characteristic
of applicational significance to medium-term earthquake prediction with a time scale of two or three years.
The English version is improved by Prof. Xin-Ling QIN, Institute of Geophysics, SSB, China. 相似文献
8.
GUO Zeng-Jian 《地震学报(英文版)》2000,13(4):477-480
IntroductionIn the book Future CataS~ologr published in 1992, we proposed a viewpoiflt on using the"criterion of activity in quiescence" to predict big eathquake (MsZ7) (GUO, et al, 1992), and predicted in the book that in futore several years or in ten years a big earthquake (Ms27) will be possible to occur in the Zhongdian and nearby in Yunnan Province. In the 1994 nation-wide earthquake tendency consultation meeting we pointed out, once more, in the Zhongdian region of Yunnan Province… 相似文献
9.
本文利用中国数字测震台网和流动台站的地震资料,基于参数优化的AICD自动拾取算法和质量评估方案得到了高质量的震相到时,并在此基础上使用一维、三维定位方法对腾冲地区的799次地震事件进行了重新定位。定位结果显示:水平方向上,一维、三维重定位结果相差较小;深度方向上,三维定位的震源成丛分布比一维定位结果更加密集,地震主要位于地壳内低速层之上。分别利用一维、三维定位方法对典型地震、人工震源进行定位,结果表明,三维定位的精度明显优于一维定位,其在水平、深度方向上的平均绝对定位误差分别为0.7 km和1.3 km。 相似文献
10.
A neural network system for P and S-picking and location of earthquakes in Northeastern Italy is described. It is applied to 7108 seismograms corresponding to 1147 earthquakes occurring in Northeastern Italy and surrounding area in the period 2000–2003. Its results are compared with two sets of manual picks and with the picks performed by the existing seismic alert system. The new system recognizes 89% and 67% of P and S arrival times, respectively, which allows locating 92% of the earthquakes. P and S-picks differ from the best available manual picks by 0.00 ± 0.07 s and 0.00 ± 0.18 s, respectively. The corresponding earthquake locations differ by −0.18± 0.77 km in longitude, 0.10± 0.62 km in latitude and 0.1± 2.0 km in depth. These results suggest its use for alert purposes and rapid production of preliminary bulletins.Considering a subset of picks that are common to all the available data sets, the absolute accuracy (i.e., the inverse of the standard deviation of differences between the estimated and the true, unknown arrival times) of each picking method is estimated. The best available manual data set has standard deviation 0.03 s for P waves and 0.07 s for S waves, while for the new system it is 0.06 s and 0.18 s for P and S waves, respectively.This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to Journal of Seismology. 相似文献
11.
Time-dependent models for seismic hazard and earthquake probabilities are at the leading edge of research nowadays. In the
framework of a 2-year national Italian project (2005–2007), we have applied the Brownian passage time (BPT) renewal model
to the recently released Database of Individual Seismogenic Sources (DISS) to compute earthquake probability in the period
2007–2036. Observed interevent times on faults in Italy are absolutely insufficient to characterize the recurrence time. We,
therefore, derived mean recurrence intervals indirectly. To estimate the uncertainty of the results, we resorted to the theory
of error propagation with respect to the main parameters: magnitude and slip rate. The main issue concerned the high variability
of slip rate, which could hardly be reduced by exploiting geodetic constraints. We did some validation tests, and interesting
considerations were derived from seismic moment budgeting on the historical earthquake catalog. In a time-dependent perspective,
i.e., when the date of the last event is known, only 10–15% of the 115 sources exhibit a probability of a characteristic earthquake
in the next 30 years higher than the equivalent Poissonian probabilities. If we accept the Japanese conventional choice of
probability threshold greater than 3% in 30 years to define “highly probable sources,” mainly intermediate earthquake faults
with characteristic M < 6, having an elapsed time of 0.7–1.2 times the recurrence interval are the most “prone” sources. The
number of highly probable sources rises by increasing the aperiodicity coefficient (from 14 sources in the case of variable
α ranging between 0.22 and 0.36 to 31 sources out of 115 in the case of an α value fixed at 0.7). On the other hand, in stationary time-independent approaches, more than two thirds of all sources are
considered probabilistically prone to an impending earthquake. The performed tests show the influence of the variability of
the aperiodicity factor in the BPT renewal model on the absolute probability values. However, the influence on the relative
ranking of sources is small. Future developments should give priority to a more accurate determination of the date of the
last seismic event for a few seismogenic sources of the DISS catalog and to a careful check on the applicability of a purely
characteristic model. 相似文献
12.
The 2009 L’Aquila, Italy earthquake highlighted the seismic vulnerability of historic masonry building structures due to improper "strengthening" retrofit work that has been done in the last 50 years. Italian seismic standards recommend the use of traditional reinforcement techniques such as replacing the original wooden roof structure with new reinforced concrete (RC) or steel elements, inserting RC tie-beams in the masonry and new RC floors, and using RC jacketing on the shear walls. The L’Aquila earthquake revealed the numerous limitations of these interventions, because they led to increased seismic forces (due to greater additional weight) and to deformation incompatibilities of the incorporated elements with the existing masonry walls. This paper provides a discussion of technical issues pertaining to the seismic retrofit of the Santa Maria di Collemaggio Basilica and in particular, the limitations of the last (2000) retrofit intervention. Considerable damage was caused to the church because of questionable actions and incorrect and improper technical choices. 相似文献
13.
In this paper, we show how to estimate the phase velocities of multi-mode signals as present in 2-D shallow seismic surveys
along a seismic line with the help of a method that is based on the deformation of the wavelet spectra of the seismic traces.
In analogy with frequency-wavenumber (f–k) analysis, we perform “frequency-velocity” analysis using the correlations between phases of the wavelet spectra. Our method
has two tuning parameters — the parameter of an analyzing wavelet and the parameter of a threshold operation. Numerical and
experimental examples are presented to illustrate how the method accurately extracts the phase velocity from single- and multi-mode
signals. 相似文献
14.
The specialized station of high-frequency seismic noise registration “Nachiki” is described arranged on Kamchatka in 1987.
The instrument-methodical aspects of registration are considered, as well as history of observations development. New principal
experimental results of surveys are represented. The results of use of high-frequency seismic noises are summarized to reveal
strong earthquake precursors in the online mode in 1996–2008. 相似文献
15.
We computed a one-dimensional (1D) velocity model and station corrections refering to the Provence region (South-eastern France) by inverting P-wave arrival times recorded on an eight-station local seismic network. Using this velocity model and the program HYPOELLIPSE (Lahr, 1989), we relocated a set of 108 local events. The quality comparison between previous earthquake locations and new relocated shows a good improvement.The obtained Minimum 1D velocity model can be used in a better-quality routine for earthquake location and represent a first step towards more detailed seismic studies in the Provence region. 相似文献
16.
Rigid sliding block analysis is a common analytical procedure used to predict the potential for earthquake-induced landslides
for natural slopes. Currently, predictive models provide the expected level of displacement as a function of the characteristics
of the slope (e.g., geometry, strength, yield acceleration) and the characteristics of earthquake shaking (e.g., peak ground
acceleration, peak ground velocity). These predictive models are used for developing seismic landslide hazard maps which identify
zones with risk of earthquake-induced landslides. Alternatively, these models can be combined with Shakemaps to generate “near-real-time”
Slidemaps which could be used, among others, as a tool in disaster management. Shakemaps (a publicly available free service
of the United States Geological Survey, USGS) provide near-real-time ground motion conditions during the time of an earthquake
event. The ground motion parameters provided by a Shakemap are very useful for the development of Slidemaps. By providing
ground motion parameters from an actual earthquake event, Shakemaps also serve as a tool to decouple the uncertainty of the
ground motion in sliding displacements prediction. Campania region in Italy is studied for assessing the applicability of
using Shakemaps for regional landslide-risk assessment. This region is selected based on the availability of soil shear strength
parameters and the proximity to the 1980 Irpina (M
w
= 6.9) Earthquake. 相似文献
17.
Using ground temperature data from meteorological stations as well as earthquake, ground tilt and precipitation data, the
spatial-temporal distribution of “Underground Hot Vortex” (UHV) in China was analyzed in detail. The results show that concerning
an “Underground Hot Vortex” cell, its life-span is 3–8 seasons, 1.5 years on average; the mean horizontal scale is 600 km
and its characteristic velocity is about 400 km/a; UHV is likely to appear in some areas where the crustal movement is intense
and the absolute value of vertical deformation rate is relatively high; its activity could hardly be detected in the area
where the crust is stable and the vertical deformation is weak; most of “Underground Hot Vortex Groups” originate from the
edge of Indian Plate, then migrate eastwards with a leaping-frog style. 5–10 years are needed for their arrival in the eastern
border of China. Their horizontal migrating velocity is 200–500 km/a which is nearly equal to the characteristic velocity
of a single UHV.
Project sponsored by the National Climbing Project and Key Project of the Chinese Academy of Sciences. 相似文献
18.
Study on the pattern and mode of vertical crustal deformation during the seismogenic process of intraplate strong earthquakes 总被引：3，自引：0，他引：3
Ｓｔｕｄｙｏｎｔｈｅｐａｔｔｅｒｎａｎｄｍｏｄｅｏｆｖｅｒｔｉｃａｌｃｒｕｓｔａｌｄｅｆｏｒｍａｔｉｏｎｄｕｒｉｎｇｔｈｅｓｅｉｓｍｏｇｅｎｉｃｐｒｏｃｅｓｓｏｆｉｎｔｒａｐｌａｔｅｓｔｒｏｎｇｅａｒｔｈｑｕａｋｅｓ杨国华，桂昆长，巩曰沐，杨春花，韩... 相似文献
19.
A three-component geomagnetic survey was carried out during the period from 2002 to 2004 in China including Jiujiang-Ruichang region. Comparing the ＂2005.0 surface spline model of China geomagnetic field＂ created on the basis of the survey data with the ＂1970.0 surface spline model of China geomagnetic field＂, we can see an obvious abnormity in the geomagnetic horizontal component within a range of about 100 km around the epicenter of the Ms=5.7 Jiujiang-Ruichang earthquake occurred on November 26, 2005. After the earthquake, we carded out a repeated geomagnetic survey at 21 stations in the Jiujiang-Ruichang region and created a corresponding ＂2005.0 partially revised surface spline model of China geomagnetic field＂. By comparing the above three models, analyzing the geomagnetic horizontal component at the profile in the Jiujiang-Ruichang region and quantitatively studying the geomagnetic data of every stations around the Ms=5.7 earthquake, we have obtained the geomagnetic abnormity associated with this earthquake. Then the geomagnetic abnormity and its relation with seismic activity are discussed in this paper. 相似文献
20.
The geography information system of the 1303 Hongton M=8 earthquake has been established. Using the spatial analysis function of GIS, the spatial distribution characteristics of
damage and isoseismal of the earthquake are studies. By comparing with the standard earthquake intensity attenuation relationship,
the abnormal damage distribution of the earthquake is found, so the relationship of the abnormal distribution with tectonics,
site condition and basin are analyzed. In this paper, the influence on the ground motion generated by earthquake source and
the underground structures near source also are studied. The influence on seismic zonation, anti-earthquake design, earthquake
prediction and earthquake emergency responding produced by the abnormal density distribution are discussed.
Foundation item: National important fundamental research “The Basic Research of Important Project in Damage Environment” and The important
project “The Seismic Hazard Assessment Research and Anti-earthquake Structure Research” from China Earthquake Administration
during the 10th Five-year Plan.
Contribution No. 04FE1008, Institute of Geophysics, China Earthquake Administration. 相似文献