Focus-of-attention techniques in the automatic interpretation of seismograms     

Claudio Chiaruttini 《Pure and Applied Geophysics》1991,135(1):61-75

The focus-of-attention techniques implemented in SNA2, a knowledge-based system for seismogram interpretation, are presented. They consist of data compression of the input digital records, scanning of the compressed traces to detect candidate seismograms and extraction of seismogram features. A criterion is given to rate the clarity of seismograms; the clarity defines the order in which the system will consider them to build up the interpretation. The proposed techniques are simple and fast; they allow quick rejection of noise and focussing the attention of the system on the portions of traces containing relevant information.  相似文献   

The gross features of the lithosphere-asthenosphere system in Europe from seismic surface waves and body waves     

G. F. Panza  St. Mueller  G. Calcagnile 《Pure and Applied Geophysics》1980,118(2):1209-1213

Long-period recordings of dispersive Rayleigh waves along numerous station lines, or profiles, in Europe have for the first time permitted a uniform inversion of these observations based on a new method of phase velocity regionalization.Regional dispersion relations obtained by this method have then been subjected to a complete inversion procedure commonly known as the hedgehog method. The results are presented in a map outlining the thickness of the lower lithosphere (lid) and the shear (S) velocities in both the lid and the asthenosphere channel.A comparison of these results with the minimum compressional (P) wave velocities in the asthenosphere and their corresponding depths provides an estimate of theV _p /V _s ratio for the asthenosphere in the European area.Contribution No. 314, Institute of Geophysics, ETH-Zürich, Switzerland.  相似文献   

地震学进展     

陈Yong 《地球物理学进展》1993,8(1):9-17

简要回顾了当代地震学发展的两个方面,一是利用地震波探测地球内部.包括:现代测震技术的发展、数字地震学、地震层析成象、地震勘探和地下核爆炸侦查等;二是研究天然地震的成因以及地震灾害的预测和预防,包括:考古地震学的发展,地震活动的统计特征,地震模型、中长期地震预报等.  相似文献   

某些地震学预报方法的分类及初步优选   总被引：3，自引：0，他引：3  

刁守中  华爱军  郭爱香 《内陆地震》2000,14(1):15-23

根据地震学预报方法及参数的物理意义、统计特征及相互关系,按其描述的地震现象或介质特性,将这些方法和参数分为空间结构、时间结构、震级结构、外因调制、震源及介质、综合民生参数及地震序列参数７大类。部分参数间具有相关性,不必重复使用。通过对以地震目录为基础资料的某些地震学参数算法分析及地震学意义的讨论,初步优选了相关姘变为：研究地震空间结构,可使用Ｄs、Ｑn或Ｃ值之一;研究地震时间结构,使用Ｎ、Ｄ或βn之  相似文献   

An upper mantleP-wave velocity model for eastern and southern Africa     

A. G. Green 《Pure and Applied Geophysics》1978,116(6):1262-1273

AP-wave velocity model for the upper mantle beneath eastern and southern Africa is proposed. The top 250 km of the model is characterized by relatively low velocities similar to those deduced for the upper mantle beneath the western United States of America. At greater depths, the velocities gradually change to normal mantle values.  相似文献   

Higher mode dispersion measurement     

G. F. Panza  G. Scalera 《Pure and Applied Geophysics》1978,116(6):1274-1283

A new method is presented for the determination of higher mode dispersion over small distances, using two stations.From an intermediate focus earthquake it has been possible to measure the dispersion of the first and second Rayleigh modes in the period range 25–35 sec and 25–70 sec respectively.Using the almost linear array of Italian long-period stations TRI, BLZ, OLB an estimate of the average errors is also made.Pubbl. No. 42 of P. F. Geodinamica-CNR-Roma.  相似文献   

Evidence for lithospheric detachment in the central Andes from local earthquake tomography   总被引：4，自引：1，他引：3  

B. Schurr  A. Rietbrock  G. Asch  R. Kind  O. Oncken   《Tectonophysics》2006,415(1-4):203-223

Data from three temporary seismic networks were merged for tomographic inversion. Although the deployments did not coincide in time, spatial overlap was achieved by re-occupying existing sites. Travel times and t operators of about 1600 earthquakes were inverted for 3D models of ν_p, ν_p/ν_s and P-wave attenuation (Q_p^− 1). All three attributes provide a consistent image of the entire subduction zone on a lithospheric scale. The tomographic images reveal low velocities and high attenuation in the crust and mantle underlying the Western Cordillera and most of the Puna plateau, indicative of weak rheology and mostly asthenospheric mantle. In contrast, forearc and eastern foreland are characterized by high Q_p values, corresponding to cold temperatures in accordance with thermal models. In the backarc, between 23°S and 24°S, a high velocity, high Q_p structure beneath the Eastern Cordillera and eastern Puna is interpreted as detaching continental lithosphere that has been thickened in the orogenic process. South of this structure, the mantle is characterized by low velocities, high ν_p/ν_s ratios, and low Q_p values. Here it is believed that lithosphere originally underlying Andean crust has already been removed. This is supported by new estimates of crustal thickness and volcanic activity.  相似文献   

A new formalism for the effect of lateral heterogeneity on normal modes and surface waves—I: isotropic perturbations, perturbations of interfaces and gravitational perturbations     

Roel Snieder  Barbara Romanowicz 《Geophysical Journal International》1988,92(2):207-222

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Fault geometries illuminated from seismicity in central Taiwan: Implications for crustal scale structural boundaries in the northern Central Range     

Jonathan R. Gourley  Timothy Byrne  Yu-Chang Chan  Francis Wu  Ruey-Juin Rau   《Tectonophysics》2007,445(3-4):168-185

Data sets of collapsed earthquake locations, earthquake focal mechanisms, GPS velocities and geologic data are integrated to constrain the geometry and kinematics of a crustal block within the accreted continental margin rocks of Taiwan's northeastern Central Range. This block is laterally extruding and exhuming towards the north-northeast. The block is bound on the west-southwest by the previously recognized Sanyi–Puli seismic zone and on the east by a vertical seismic structure that projects to the eastern mountain front of the Central Range. Focal mechanisms from the Broadband Array of Taiwan Seismicity (BATS) catalog consistently show west-side-up reverse displacements for this fault zone. A second vertical structure is recognized beneath the Slate Belt–Metamorphic Belt boundary as a post-Chi-Chi relaxation oblique normal fault. BATS focal mechanisms show east-side-up, normal displacements with a minor left-lateral component. The vertical and lateral extrusion of this crustal block may be driven by the current collision between the Philippine Sea Plate and the Puli basement high indenter on the Eurasian Plate and/or trench rollback along the Ryukyu subduction zone. In addition, the vertical extent of the two shear zones suggests that a basal décollement below the eastern Central Range is deeper than previously proposed and may extend below the brittle–ductile transition.  相似文献   

Tomographic inversion of P410s delay times for simultaneous determination of P and S velocities of the upper mantle beneath the Baltic Shield     

Sverker Olsson  Roland G. Roberts  R. Böðvarsson 《Physics of the Earth and Planetary Interiors》2007,160(2):157-168

Teleseismic data recorded by stations in the Swedish National Seismic Network (SNSN) are used for a study of upper mantle structure beneath the Baltic Shield using the receiver function technique. The data show very clear conversions from the 410 and 660 km discontinuities. The signals associated with P to S conversions at these discontinuities arrive 1-2 s earlier than predicted by global models such as IASP91 or PREM. We interpret this as a manifestation of higher than average velocities in the mantle beneath the shield, consistent with lower than average global temperatures. For a 1400 km profile along the network, we observe variations of around 1 second in delay times of P410s and slightly less for P660s. Under the assumption that the mantle discontinuities are at a given constant depth, the delay times of the mantle converted phases are tomographically inverted to reveal P and S velocity structure below the stations. Synthetic tests show that this tomographic inversion has the potential to resolve P and S velocity variations at structural scales adequate for upper mantle studies. Results from application to real data appear to be consistent with independently produced mantle velocity structures deduced from normal tomographic arrival time data. For the P velocity model, a north-dipping body of (relatively) low velocity is found for the central part of the profile at 58-64°N. A sharp contrast from low to high velocities that may be associated with the Proterozoic-Archean boundary is found at 66°N.  相似文献