秦建业
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- 姓名:秦建业
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博士生导师
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勘探地球物理学
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Kin-Yip Chun studied Engineering Science at University of Toronto (B.Sc.), and seismology at Columbia University (MA) and UC Berkeley (Ph.D.). After a brief stint at Lawrence Berkeley National Laboratory, he returned to Canada to teach at his alma Mater. Professor Chun developed and applied a rudimentary concept of tomography to the study of the Tibetan lithosphere, in 1970s, at the dawn of seismic tomography. His Ph.D. research focused on advanced signal processing and modeling of higher-mode dispersion data from the Basin and Range Province in United States. His work in 1980s gave birth to novel methods for measuring regional phase attenuation. Impervious to site response, source radiation and instrumental errors, his methods yield accuracy unsurpassed to this day. He helped Canada become a world leader in nuclear test ban verification research. He was Principal Scientific Advisor to the Canadian Delegation at the United Nations Conference on Disarmament in Geneva, where he delivered a keynote speech on global security. In 1990s Chun and his team ushered in the era of Hypereikonal, demonstrating the failures of ray theory and its modern derivatives at seismic frequencies and shedding light on the physics of wave phenomena in inhomogeneous media (e.g., evanescence of caustics, frequency-dependent raypath/wavefront). Capitalizing on earthquake multiplets, Chun’s recent invention allows him to transform earthquake rupture zones into natural laboratories for monitoring changes in pore fluid saturation, thereby opening the door to deterministic earthquake prediction. Note that: a) pore fluids are ubiquitous in fault zones of big crustal earthquakes; b) temporal changes in fault zone Q (due to fluid saturation changes), having signal amplitudes up to 100% of their ambient level, can be detected most reliably; c) time history of pore-fluid-induced Q changes prior to the occurrence of a mainshock (catastrophic rock failure) is well known from laboratory studies of rock physics. Dr. Chun is Professor of Seismology at Tongji University and the University of Toronto in Ontario, Canada.
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【期刊论文】Nuclear Test Ban Verification:Recent Canadian Research in Forensic Seismology
秦建业
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-1年11月30日
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秦建业
Geophys, 2005, 48 (4): 851-860,-0001,():
-1年11月30日
地震预测是地震学研究一个基本目标,而理解地震周期是地震预测的重要环节。遗憾的是,由于地震断层 带不但结构复杂,大地震前后短时问内的震源过程更是随时间迅速变化。这复杂因素使得常规研究方法不再适 用。一类特殊的微震成群地发生在主震断层几乎同一地点上,震源系数几乎相同,近年来地震学界通称其为震群(earthquake multiplet)。本文论证如何将这类特殊的微震作为一组人工震源来阐述美国西部两次大地震(Loma Prieta 和Morgan Hill)的震后弛豫过程。在加利福尼亚Loma Prieta(1989年9月18日,M7.0)及Morgan Hill(1984年4月24日,M6.2)附近的主震破裂带中的发生了此类震群。其中有两组各包含11个重复地震的震群,分别位于这两个破裂带中,其波形资料质量高,波形及震级变化极小,因而可与实验室条件下的人工震源相比。这些震群地震资历料可直接用于计算P波沿波程衰减(即t*)的时间性变化,其方法的简单性及结果的精确性都与实验室水平相当。我们的结果显示,每个震群周围分别存在一个异常体,在其各自主震之后的10个月中,该异常体中的P波衰减迅速上升并降落。衰减峰值发生在Loma Prieta地震后2~3周,其震群深度为10.2km。此峰值在Morgan Hill地震后5~6个月发生,其震群中心深度为2.6km。这两个事例中,t*波动峰值都超过此前获得的加利福尼亚大致同一地区t*绝对值的100%[1]。此结果显示了因同震裂隙张开和震后弛豫过程(如流体移动、裂隙复原及岩石压缩),以及孔隙度和流体饮和度在主震体部分区域发生的变化。衰减达峰值的时间之显著差异则提示我们,裂隙闭合及伴随的流体移动是负载敏感的,深度越大达峰值越快,反之就亦然。如将此方法应用于主震前多重地震的资料,将有望好地理解最终导致主震断层带大破裂的震前微破裂的物理过程。
P减衰减,, 时间性变化,, 破裂带,, 孔隙度,, 流体移动
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【期刊论文】Complex rays in elastic and anelastic media
秦建业, Tianfei Zhu and Kin-Yip Chun
Geophys J. Int. (1994) 119, 269-276,-0001,():
-1年11月30日
The concept of complex rays plays an important role in wave-propagation modelling. In this study we describe an eh~cient method for complex ray tracing. Our objective is to facilitate generalization of this concept to wave-propagation studies in general inhomogeneous media. By solving rigorously the complex eikonal equation arising from medium anelasricity, we strive to provide an accurate description of the wave-attenuation process in a realistic earth structure. To enhance practical utility of our method, we have developed a ray-perturbation scheme which keeps the computation to a minimum. A further advantage of our approach is that it can be used to extend the technique of complex source point to general inhomogeneous media. The said extension overcomes the singularity problem encountered by asymptotic ray theory near a caustic and is capable of modelling evanescent waves.
anelasticity,, body waves,, complex ray,, complex source point,, perturbation.,
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秦建业, KIN-YIP CHUN, TIANFEI ZHU AND GORDON F. WEST
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 98, NO.B6, PADGES 9927-9929, JUNE 10, 1993,-0001,():
-1年11月30日
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秦建业, Tianfei Zhu and Kin-Yip Chun
Geophys. J. Int. (1994) 119, 78-90,-0001,():
-1年11月30日
A straight line connecting two points in a homogeneous elastic medium defines a body-wave ray path. A single wavefront can be said to be uniquely associated with a body-wave signal propagating along this path. Ray path and wavefront are concepts at once straightforward and useful in such media, where exact solutions may be attainable. In inhomogeneous media, signal distortions accompany the physical processes of focusing/defocusing and scattering. The ray path depends on the signal frequency; the very concept of a single waveffont for each propagating body wave is blurred. To assume otherwise is tantamount to neglecting a host of wave phenomena intrinsically connected with the scattering effects due to medium inhomogeneities. An example of such a scattering-related wave phenomenon is frequency-dependent partial reflection of a body wave propagating in a zone of hlgb-velocity gradient. These phenomena are not modelled by the published ray methods for seismic wavefield computation, limiting their applicability to homogeneous and weakly inhomogeneous media. The scattering-induced wave phenomena become increasingly more difficult to ignore as the wave-medium heterogeneity strengthens. To achieve a higher order of accuracy than the published ray melhods, it is necessary to incorporate the scattering effects. The principal objective of this study is 1o extend our wavefieldmodelling capability to rapidly varying media by proper accounting for the scattering effects embodying, among others, frequency-dependent ray paths and scatteringinduced wave attenuation and dispersion. We demonstrate that the new formulation based on a phase eikonal equation can now model frequency-dependent partial reflections from a gradient zone. It is shown that the scattering process introduces signal smoothing and its incorporation in the wavefield calculation results in natural removal of the singularity of asymptotic ray theory near a caustic.
caustic,, inhomogeneity scattering,, perturbation,, phase eikonal,, phaseray method,, scattering related wave phenomena.,
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秦建业, KIN-YIP CHUN, TIANFEI ZHU, AND GORDON F. WEST
JOURNAL OF GEOPHYSICAL RESEARCH. VOL.96, NO.B7, PAGES 12, 083-12,097, JULY 10, 1991,-0001,():
-1年11月30日
We report here the results of a comprehensive seismic attenuation ivestigation along the paths connecting Canada's Yellowknife seismic array (YKA) with seven active nuclear explosion testing areas. The data conisst of more than 600 explosion-generated teleseismic P wave records. A dual time-frequency averaging ttechnique is used to take advantage of the array recording characteristics without the drawback of the conventional is used to take advantage of the array recording chanracteristics without the drawback of the conventional beam-forming, excessive annihilation of high-frequency signal energies. The dual averaging technique, deployed in conjunction with a multiwindow spectral analysis method, yields smooth amplitude spectra whose falloff at high frequencies suffers little from spectral leakage due to hte familiar presence of a prominent low-frequency plateau. Measured in terms of t*, the highest attenuation (0.66s) is found along the path withich originates forom the Tuanmotu test area; somewhat less attenuating are the two paths which depart from the Pahute Mesa (0.59s) and Yucca Flat (0.50s) nuclear test areas, bnoth located within the U.S. Nevada Test Site. We find t* for et al., 1985). We attribute these disparities largely to differences in spectral leakage control capability between the conventional single window and the improved multiwindow spectral analysis methods. The least attenuating paths all originate from the Soviet test areas: Novaya Zemlya (NZ). west Kazakhstan, Degelen Mountain (DM). ans Sjhagan River (SR). The last two of these test areas, DM and SR, are both located in east Kazakhstan. The P wave signatures of the Soviet explosions are rich in high-frequency (>4.5 Hz) energies, and the YKA data (0.5-8.0 Hz) support a frequency-dependent t* whose value at high frequencies (>4.5 Hz) is as small as 0.17s. To gain a grasp of the ramifictions of the t* disparity between te multiple-window and the single-window results, we have compared explosion source time functions obtained by the multichannel deconvolutioon technique of Shumway and Der (1985)in order to assess their sensitivity to the input t* value. In our example involving the deconvolved sourece functions of cfive French Tuamoutu explosions, we find that a 0.1-s t* difference is large enough to cause clearly discernible signature differences, in terms of the signal frequency content as well as the extractability of a s secondary arrival some .4 s behind the first P arrival. This secondary arrival is belived to be the depth phase pP, a seismic signature of importance in both yield estimation and earthquake/explosion source discrimination. The absorption band modeling (Minsterm, 1978a, b) of ethe French Tuamotu explosion data yields 1.8
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【期刊论文】Pn波的形成及其衰减特征—对加拿大地盾的研究1)
秦建业, 朱天飞, G.F. West
地球物理学报,1991,34(5):563~568,-0001,():
-1年11月30日
尽管Pn波品质因子(PaQ)对上地幔流变性质研究及核试验监测有着深刻含义,迄今它仍然是一个难以准确测定的地震参量。这是因为除了众所周知的影响所有短周期Q的干扰因素外,在昕有主要的区域震相中,地震工怍者对Pn波的传播模式及几何扩散函数G=d-k中的扩散串指数k了解最少。不同的研究者任意地假定不同的常数k,因此常算出非常不同的PnQ值(例如文献[1]、[2])实际上,理论研究已表明,k随频率而变,变化的形式取秩于上地幔的速度结构[3,4]。本文介绍用一推广的逆向双台法同时测定加拿大东部的PnQ和k值。我们的结果表明:1. 加拿大东部的Pn波是由一系列的干涉潜波叠加而形成;2. 视PnQ(散射和固有非弹性的综合效应)随频率而增加,在15Hz处接近2000。
Pn衰减,, 与频率有关的几何扩散,, 逆向双台法.,
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【期刊论文】Temporal changes in P wave attenuation in the Loma Prieta rupture zone
秦建业, Kin-Yip Chun, Gary A. Henderson, and Jingsong Liu
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, B02317,-0001,():
-1年11月30日
[1] Clusters of recurring, nearly identical microearthquakes have been recorded near Loma Prieta, California. Such events make possible direct measurement of temporal changes in the attenuation operator t* along fixed paths under what are tantamount to laboratory conditions. Analysis of almost 10 years of P wave data following the 18 October 1989 Loma Prieta, California, main shock (M=7.0) reveals a large-amplitude t* increase within the first 3 weeks of the main shock. A gradual t* recovery toward its level prior to the main shock is seen in the years ensuing. The results point to changes in porosity and fluid saturation taking place in parts of the main shock source volume, stemming from coseismic crack opening and postseismic relaxation processes such as postseismic fluid flow into the cracks, crack healing, and rock compaction.
Loma Prieta rupture zone,, postseismic relaxation,, time-dependent t*,
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【期刊论文】CRUSTAL BLOCK OF THE WESTERN GANGA BASIN: A FRAGMENT OF OCEANIC AFFINITY?
秦建业, BY KIN-YIP CHUN
Bulletin of the Seismological Society of America, Vol. 76, No.6, pp. 1687-1698, December 1986,-0001,():
-1年11月30日
Three-component, long-period New Delhi records of two earthquakes occurring near Multan, central Pakistan, are used to determine group velocities of multimode surface waves in the period range of 5 to 57 sec. Inversion of these data has provided insight regarding the crustal shear velocity structure in the western Ganga Basin, in the northwestern wedge of the Indian subcontinent. The shear velocity is less than 3.10 km/sec within the topmost 10 km of its 40-km-thick crust. The estimated velocity in the 10-to 20-km depth range is 3.80
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【期刊论文】HIGH-FREQUENCY P-WAVE ATTENUATION DETERMINATION USING MULTIPLE-WINDOW SPECTRAL ANALYSIS METHOD
秦建业, BY TIANFEI ZHU, KIN-YIP CHUN, AND GORDON F. WEST
Bulletin of the Seismological Society of America, Vol. 79, No.4, pp. 1054-1069, August 1989,-0001,():
-1年11月30日
Yellowknife array (Northwest Territories, Canada) recordings of nuclear explosions detonated at French Tuamotu, South Pacific and Shagan River, Eastern Kazakhstan (USSR) test sites are used to derive t* values via the application of the spectral decay method. An important factor that limits the reliability of this widely used method is the degree of accuracy with which one is able to determine the signal spectral shape. For transient, pulse-like, short-period teleseismic phases, the conventional single-window spectral estimate methods may not be appropriate due to the trade-off betgween the leakage resistance and variance. A recently developed, multiple-window spectral analysis method is used in this study to effectively control spectral leakage, a capability that is especially important when analyzing seismic data characterized by a rapid high-frequency fall-off rate, such as the French Tuamotu explosion data. We compare the t* estimates obtained using a conventional single-window method with those obtained using the multiple-window method and show that the latter are more reliable. The f* (0.5 to 4.5 Hz) found by the multiple-window method for the Tuamotu-Yellowknife path is 0.66 sec. For the Eastern Kazakhstan-Yeliowknife path, the multiple-window t* estimate is 0.42 sec in the 0.5 to 4.5 Hz range; a smaller value is obtained at higher frequencies (4.5 to 8 Hz).
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