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1.
Relocation of hypocenters from DOMERAPI and BMKG networks: a preliminary result from DOMERAPI project 
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下载免费PDF全文 Mohamad Ramdhan Sri Widiyantoro Andri Dian Nugraha Jean-Philippe Métaxian Asep Saepuloh Said Kristyawan Andry Syaly Sembiring Agus Budi Santoso Antoine Laurin Ahmad Ali Fahmi 《地震科学（英文版）》2017,30(2):67-79
Merapi volcano located in central Java, Indonesia, is one of the most active stratovolcanoes in the world. Many Earth scientists have conducted studies on this volcano using various methods. The geological features around Merapi are very attractive to be investigated because they have been formed by a complex tectonic process and volcanic activities since tens of millions of years ago. The southern mountain range, Kendeng basin and Opak active fault located around the study area resulted from these processes. DOMERAPI project was conducted to understand deep magma sources of the Merapi volcano comprehensively. The DOMERAPI network was running from October 2013 to mid-April 2015 by deploying 46 broad-band seismometers around the volcano. Several steps, i.e., earthquake event identification, arrival time picking of P and S waves, hypocenter determination and hypocenter relocation, were carried out in this study. We used Geiger’s method (Geiger 1912) for hypocenter determination and double-difference method for hypocenter relocation. The relocation result will be used to carry out seismic tomographic imaging of structures beneath the Merapi volcano and its surroundings. For the hypocenter determination, the DOMERAPI data were processed simultaneously with those from the Agency for Meteorology, Climatology and Geophysics (BMKG) seismic network in order to minimize the azimuthal gap. We found that the majority of earthquakes occurred outside the DOMERAPI network. There are 464 and 399 earthquakes obtained before and after hypocenter relocation, respectively. The hypocenter relocation result successfully detects some tectonic features, such as a nearly vertical cluster of events indicating a subduction-related backthrust to the south of central Java and a cluster of events to the east of Opak fault suggesting that the fault has an eastward dip. 相似文献
2.
使用基于机器学习构建的贵州西部多流域水库区地震目录和震相报告,采用波速比一致性约束的双差层析成像方法联合反演得到了该地区的地震位置和三维vp、vs、vp/vs结构。结果显示,研究区内的地壳速度结构具有明显的不均匀性,不同大地构造变形分区展现出不同的速度结构特征。在10km以上深度,横穿黔西中部NW向的威宁构造变形区显示出显著的低速异常条带,揭示了威宁—水城深大断裂带的影响深度和范围。受库区岩性和流体渗透的影响,0km深度的速度结构显示普遍的低波速和高波速比特征,包括夹岩、平寨、光照和马马崖水库区域。重定位后,地震的空间分布勾勒出大量隐伏断层的几何展布特征,结合三维速度结构,推测该区域的地震活动与水库周围的断层活化有关。 相似文献
3.
The derivation of P and S velocities at the core-mantle boundary (CMB) from long-period diffracted waves by the use of the simple ray-theoretical formulav
CMB=r
c
/p (v
CMB=velocity at the CMB;r
c
=core radius;p=ray parameter) yields apparent velocity values which differ from the true velocities. Using a dominant period of about 20 sec for calculating theoretical seismograms, we found a linear relation between the apparent velocity and the average velocity in a transition zone at the base of the mantle with fixed velocity on top.The ray parameters determined from long-period earthquake data are found to be 4.540±0.035 and 8.427±0.072 sec/deg for Pdiff and Sdiff, respectively. These values yield apparent velocities of 13.378±0.103 for P and 7.207±0.062 km/sec for S waves. By means of the theoretical relation between apparent and average velocity and under the assumption of linear variation of velocity with depth, one can invert the apparent velocities into true CMB velocities of 13.736±0.170 and 7.320±0.124 km/sec. These results imply positive velocity gradients at the base of the mantle and hence no significant departures from adiabaticity and homogeneity.Contribution No. 211 of the Geophysical Institute, University of Karlsruhe. 相似文献
4.
N. D. Delibasis 《Pure and Applied Geophysics》1982,120(4):820-839
A detailed study of P and S waves from earthquakes located along the Hellenic arc and recorded by the Greek seismological network, shows an abnormal distribution of the seismic waves in the central Aegean Sea. The data indicate a zone of anomalously high seismic wave attenuation in the Upper Mantle beneath the Cyclades plateau and the inner part of the volcanic arc. Several independent observations suggest the presence of magma beneath the Cyclades massif.In addition, geophysical data indicate the presence of low-density and rigidity material. Theoretical consideration of the propagation of elastic waves corroborate the observed absence of shear waves. 相似文献
5.
选取2009~2014年发生在云南地区、每个地震均在10个以上台站有记录的7412个地震数据,作走时曲线。同时为提高精度,重点对其中每个地震均在80%以上台站有记录的、ML≥3.0的83个地震数据,再作线性分析、折合走时曲线和区间稳定性分析,结合前人研究成果得到了研究区的初始地壳速度模型。选取2010~2014年云南省内M≥3.0的200次地震,采用Hyposat批处理方法迭代初始速度模型,以及对S波作分层速度拟合,得到云南地区的地壳速度模型,即2015云南模型:v_(P1)=6.01km/s,v_(P2)=6.60km/s,v_(Pn)=7.89km/s,H_1=20km,H_2=21km,v_(S1)=3.52km/s,v_(S2)=3.86km/s,v_(sn)=4.43km/s。基于新模型的地震重定位分析表明,云南地区地震事件大多发生于20km内的上地壳;对2011年3月10日盈江M5.8和2014年8月3日鲁甸M6.5典型地震进行重定位,得出震源深度分别与精定位结果和震中强震台震源距接近,表明新的一维速度模型能更好地反映研究区平均速度结构。 相似文献
6.
利用三维地震透射观测系统所获得的莫霍界面反射波对长白山天池火山区下方上地壳的三维速度细结构进行了反演计算，得到了研究区下方地壳内不同深度的P、S波速度层析成像和VP/VS扰动分布图像，结果表明，天池火山区及其周边速度结构所呈现出的非均匀性变化与该区的地质构造和岩浆系统的存在有着密切的关系，异常变化比较明显的低P波速度异常体分布和高VP/VS扰动体意味这些介质体处在“软化高温”的状态，这与该地区广泛分布的地热异常和低Q值结构的研究结果是一致的. 相似文献
7.
G. Barberi A. Gervasi G. Neri B. Orecchio 《Physics of the Earth and Planetary Interiors》2004,147(4):297-314
27,646 P- and 15,025 S-wave readings obtained from 2238 earthquakes and 84 artificial sources were used to perform tomographic inversion of P velocity and VP/VS ratio in the crust of Calabrian Arc by Thurber’s inversion algorithm. For this investigation a seismic database with more than twelve-thousand events was built, including all local earthquake data recorded between 1978 and 2001 at all stations of the national and local networks in south Italy. Spread Function computations and checkerboard and restore tests proved higher accuracy of velocity estimates in the upper 40 km beneath Calabrian Arc compared to previous investigations in the same area. The obtained three-dimensional velocity model furnished remarkable improvement of hypocenter locations of the global earthquake dataset (RMS reduction of 38% respect to 1D locations) and greater accuracy in the definition of microplates and tectonic units in the study region. Velocity domains evidenced by our tomography correspond to tectonic units locally identified with geological methods by previous investigators and allow us to better detail their shape and geometry at depth. In particular, at a depth of about 20 km beneath Calabria we detected the deep contact between the overthrusting Tyrrhenian crust and the subducting Ionian slab, improving the accuracy of the current subduction model of the Calabrian Arc region. 相似文献
8.
印度板块向欧亚俯冲前缘位于班公—怒江缝合带附近,但是印度岩石圈地幔的俯冲形态和形变过程仍然缺乏共识,在不同地区使用不同方法获得的结果之间存在明显差异.本文使用青藏高原中部INDEPTH-Ⅲ剖面远震S波波形数据,提取走时信息,通过层析成像方法获得剖面下方S波速度扰动图像.结果显示:在班公—怒江缝合带下方100至300km深度范围内存在一个高角度(约65°)北倾的S波高速体,推测可能是回退的印度岩石圈板片或/和小规模对流引起的岩石圈拆沉后残留的印度大陆岩石圈板片. 相似文献
9.
Heavily populated by Beijing and Tianjin cities, Bohai basin is a seismically active Cenozoic basin suffering from huge lost by devastating earthquakes, such as Tangshan earthquake. The attenuation (QP and QS) of the surficial Quaternary sediment has not been studied at natural seismic frequency (1?10 Hz), which is crucial to earthquake hazards study. Borehole seismic records of micro earthquake provide us a good way to study the velocity and attenuation of the surficial structure (0?500 m). We found that there are two pulses well separated with simple waveforms on borehole seismic records from the 2006 MW4.9 Wen'an earthquake sequence. Then we performed waveform modeling with generalized ray theory (GRT) to confirm that the two pulses are direct wave and surface reflected wave, and found that the average vP and vS of the top 300 m in this region are about 1.8 km/s and 0.42 km/s, leading to high vP/vS ratio of 4.3. We also modeled surface reflected wave with propagating matrix method to constrain QS and the near surface velocity structure. Our modeling indicates that QS is at least 30, or probably up to 100, much larger than the typically assumed extremely low Q (~10), but consistent with QS modeling in Mississippi embayment. Also, the velocity gradient just beneath the free surface (0?50 m) is very large and velocity increases gradually at larger depth. Our modeling demonstrates the importance of borehole seismic records in resolving shallow velocity and attenuation structure, and hence may help in earthquake hazard simulation. 相似文献
10.
The Yangbi MS6.4 earthquake occurred on May 21, 2021 in western Yunnan, China, where moderate earthquakes strike frequently. It exhibited a typical “foreshock-mainshock-aftershock” sequence and did not occur on a pre-existing active fault. The seismogenic environment and mechanism of this earthquake have aroused considerable research attention. In this study, we obtain the three-dimensional vP, vS and vP/vS images using the vP/vS consistency-constrained double-difference tomography method, which improves the accuracy of vP/vS models. We focus on characteristics of vP/vS images in areas with a lateral resolution of 0.1°, and reveal the seismogenic environment of the Yangbi MS6.4 earthquake. The conclusions are as follows: (1) Low velocity and high-vP/vS anomalies are revealed at different depths around the northern segment of the Red River fault. vS and vP/vS images along the Weixi-Qiaohou-Weishan fault and the buried faults on its west show obviously segmented feature. (2) The source region of the Yangbi MS6.4 earthquake is located in a low-vP/vS zone implying high medium strength. High-vP/vS anomalies in its NW direction indicate cracks development and the existence of fluids or partial melts, which are unfavorable for stress accumulation and triggering large earthquakes. Such conditions have also prevented the earthquake sequence from extending northwestward. (3) With the southeastward extrusion of materials from the Tibetan Plateau, fluid migration was blocked by the low-vP/vS body in the source region. The high-vP/vS anomaly beneath the source region may implies that the fluids or partial melts in the middle and lower crust gradually weakened medium strength at the bottom of the seismogenic layer, and preparing the largest foreshock in the transition zone of high to low vP/vS. Meanwhile, tectonic stress incessantly accumulated in the brittle upper crust, eventually led to the MS6.4 earthquake occurrence. 相似文献
11.
重庆荣昌诱发地震区精细速度结构及2010年M_L5.1地震序列精确定位 总被引：1，自引：0，他引：1
根据重庆市地震台网和流动地震台网记录到的天然地震资料,利用接收函数反演得到荣昌地区的精细一维速度结构。在此基础上用双差定位法对2010年9月10日重庆荣昌M_L5.1地震序列进行了精定位。结果表明,地震定位精度得到极大提高,震中分布与区域地质构造的关系更加清晰。多数地震集中在主要断层附近并呈条带状分布,震源深度集中在2km附近,与主要储藏层及注水井深度吻合,初步认为该地震序列为注水活动所诱发的构造地震活动。文中获得的精准的速度结构及地震空间分布对于进一步深入研究震区深部地质构造特征、注水诱发地震的机理等具有重要意义。 相似文献
12.
Based on data collected from a temporal seismic network, and in addition to the data from some nearby permanent stations, we investigate the velocity structure and seismicity in the Rongchang gas field, where significant injection-induced seismicity has been identified. First, we use receiver functions from distant earthquakes to invert detailed 1-D velocity structures beneath typical stations. Then, we use the double-difference hypocenter location method to re-locate earthquakes of the 2010 ML5.1 earthquake sequence that occurred in the region. The re-located hypocenters show that the 2010 ML5.1 earthquake sequence was distributed in a small area surrounding major injection wells and clustered mostly along pre-existing faults. Major earthquakes show a focal depth less than 5km with a dominant depth of ～2km, a depth of major reservoirs and injection wells. We thus conclude that the 2010 ML 5.1 earthquake sequence might have been induced by the deep well injection of unwanted water at a depth ～3km in the Rongchang gas field. 相似文献
13.
利用布设在长白山地区的19个PASSCAL宽频带流动地震台站近一年的远震记录和布设在镜泊湖火山区14个宽频带轻便数字地震仪三个月的远震记录,共得到高质量的423个接收函数,通过对这些接收函数的共转换点叠加得到研究区的间断面的分布及形态.研究结果表明,研究区存在410、520km和660km间断面.410km和660km间断面较为连续且具有正相关性质,410km间断面在长白山天池火山下局部上隆,660km间断面具有复杂的多界面性质.410km和660km之间的过渡带厚约250km,接近全球平均水平.珲春深震区下660km界面下陷,其上还有多组震相,这些震相在珲春深震区东西两侧不连续,推测西太平洋板块至少已经俯冲到欧亚大陆下的上地幔过渡带中.410km间断面在长白山火山区下局部上隆,660km间断面具有的复杂结构和珲春深源地震的发生均与俯冲板块在过渡带中的活动有关. 俯冲板块在受到660km间断面的强大阻力后,在660km间断面之上变为近水平扩张.推测在欧亚大陆下西太平洋板块的最前端可能已经不是一个完整的整体,或许是由几个有一定联系的板块残片组成. 相似文献
14.
The July 3, 2015 Pishan MS6.5 earthquake occurred in the intersection area of the Tarim block and West Kunlun block where the moderate-strong earthquakes have become active in recent years. This paper has studied the seismicity parameters of the earthquake sequences such as the b-value in the Pishan region and its vicinity. In addition, we also relocated the aftershocks of the Pishan MS6.5 earthquake using the seismic phase report by the double-difference method. The temporal and spatial variation characteristics of the Pishan earthquake sequence in the rupture zone are analyzed. The study is of great significance in the seismic hazard assessment in this region. 相似文献
15.
本文利用2010年1月至2020年6月巧家地震和鲁甸地震震源区周围发生地震事件的走时观测资料,应用双差层析成像方法获得了2014年MS6.5鲁甸地震和2020年5月18日巧家MS5.0地震周边区域中上地壳的P波速度结构。成像结果显示:整个研究区域的速度结构存在很强的非均匀性:在鲁甸地震震源区附近,浅部存在速度高达6.4 km/s的显著高速异常,10 km深度以下存在速度低至约5.8 km/s的明显低速异常;鲁甸地震的初始破裂点位于高低速异常的过渡带;在2010年巧家MS4.8和2020年巧家MS5.0地震的震源区,尽管浅部没有显著的高速异常,但在主震的初始破裂点下方均存在明显的局部低速异常;巧家北部中上地壳存在明显低速异常。 相似文献
16.
The S wave velocity structure between the hypocenter of C060394F earthquake,South Java and a series of observatory stations located in Australia and South-East Asia have been investigated through seismogram analysis in the time domain and the three Cartesian components.The synthetic seismogram is constructed from the PREMAN global earth model.Seismogram comparison between the measured and synthetic seismograms shows large discrepancies.A correction to the S wave velocity structure is needed to solve these d... 相似文献
17.
本文联合使用云南、四川和贵州地震台网的85个地震台站在2008年1月—2017年12月期间记录的49130个地震、317366个初至Pg震相绝对到时数据和2674110条高精度的相对到时数据,采用区域双差地震层析成像方法联合反演了川滇南部地壳三维P波速度结构和39621个地震的震源参数,探究了川滇南部中下地壳流和腾冲火山区岩浆囊的分布特征.研究结果表明：（1）川滇南部上地壳的速度异常特征与地表地形密切相关;（2）小江断裂带的中下地壳存在一条绵延近二百多公里的低速异常结构,最南端受到红河断裂带的阻挡而终止于断裂带南段北侧,这可能是川滇南部的一条中下地壳流,低速异常结构在红河断裂带南段转而向南东流动反映了红河断裂带可能为川滇菱形块体的西南边界;（3）红河断裂带各段速度异常存在明显的差异,重定位后的震源分布显示红河断裂带中段和南段虽然不如北段地震活动强烈,但地震震源深度分布较北段深;（4）腾冲火山区西侧和北侧下方10~20 km深度范围内存在的低速异常体推测为通过怒江断裂带形成的岩浆通道从中地壳涌入上地壳的岩浆囊,可能反映了自更新世延续至今的以橄榄玄武岩和安山岩为主要岩性的壳内岩浆活动,持续的岩浆活动为地表热活动提供了主要动力. 相似文献
18.
《Geofísica Internacional》2014,53(2):211-220
We apply a single-step, finite-fault analysis procedure to derive a coseismic slip model for the large MW 7.4 Ometepec-Pinotepa Nacional, Mexico earthquake of 20 March 2012, using teleseismic P waveforms recorded by the Global Seismographic Network. The inversion is conducted in near-realtime using source parameters available from the USGS/NEIC and the Global Centroid Moment Tensor (gCMT) project. The fault orientation and slip angle are obtained from the gCMT mechanism assuming that the fault coincides with the shallow-dipping nodal plane. The fault dimensions and maximum rise time are based on the magnitude reported for the event. Teleseismic data from the USGS/NEIC Continuous Waveform Buffer database are used in the inversion with record start times set to the P-wave arrivals used to compute the earthquake hypocenter. The inversion is stabilized by requiring a smooth transition of slip across the fault while minimizing the seismic moment. These constraints are applied using a smoothing weight that is estimated from the inverse problem, allowing the recovery of the least-complicated rupture history in a single step. Inversion of the deconvolved, ground-displacement waveforms reveals a simple, circular rupture similar in extent to the source identified by the USGS/NEIC using body-and surface-wave data, indicating that the teleseismic P waves can provide a first-order source model for the event in near-realtime. Additional inversions conducted using velocity records identify a more-detailed rupture model characterized by an elliptical 2500 km2 source region extending updip and downdip from the hypocenter. This elliptical source preserves the orientation and overall dimensions of a dual-source slip model obtained recently by other investigators using local strong motions and global seismic waveforms. The results indicate that velocity waveforms could provide additional details of the earthquake rupture in near-realtime, finite-fault inversions using teleseismic P waves. 相似文献
19.
Jean -Luc Got Vadim Monteiller Jean Virieux Paul Okubo 《Pure and Applied Geophysics》2006,163(2-3):405-430
Seismic velocity parameters in limited, but heterogeneous volumes can be inferred using a double-difference tomographic algorithm,
but to obtain meaningful results accuracy must be maintained at every step of the computation. MONTEILLER et al. (2005) have devised a double-difference tomographic algorithm that takes full advantage of the accuracy of cross-spectral
time-delays of large correlated event sets. This algorithm performs an accurate computation of theoretical travel-time delays
in heterogeneous media and applies a suitable inversion scheme based on optimization theory. When applied to Kilauea Volcano,
in Hawaii, the double-difference tomography approach shows significant and coherent changes to the velocity model in the well-resolved
volumes beneath the Kilauea caldera and the upper east rift. In this paper, we first compare the results obtained using MONTEILLER
et al.'s algorithm with those obtained using the classic travel-time tomographic approach. Then, we evaluated the effect of using
data series of different accuracies, such as handpicked arrival-time differences (``picking differences'), on the results
produced by double-difference tomographic algorithms. We show that picking differences have a non-Gaussian probability density
function (pdf). Using a hyperbolic secant pdf instead of a Gaussian pdf allows improvement of the double-difference tomographic
result when using picking difference data. We completed our study by investigating the use of spatially discontinuous time-delay
data. 相似文献
20.
—We investigate the distribution of partial melt in island arc using the seismic velocity structure of the mantle wedge beneath northeastern Japan. The comparison of the seismic tomography with laboratory velocity data on a partially-molten mantle rock yields estimates of melting zones in three dimensions. We employ experimental data on the degree of partial melt in hydrous peridotite to give constraints on the melt fraction and temperature. Melting and magma-rich zones derived from the velocity structure coincide with observed low Q zones. The results of the three-dimensional mapping indicate that the source of magma in island arc is diapir-like melting patches localized within the low velocity zones of the mantle wedge. Extensive volcanic activity along the volcanic front is due to the presence of vast magma-rich zones just beneath the Moho. Those melting zones in the uppermost mantle may, in turn, cause melting of lower crustal materials and produce felsic magma. Melt appears to stay at and beneath the Moho, where crystallization fractionation may proceed. Melt exists at greater depths in the back-arc region, which may correlate with across-arc variations of chemical compositions of the volcanic rocks observed in northeastern Japan. We suggest that magma migration in the ductile lower crust may cause low-frequency microearthquakes, and magma penetration into the brittle upper crust may produce mid-crustal S-wave reflectors. 相似文献