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991.
992.
993.
P. A. Bedrosian N. Maercklin U. Weckmann Y. Bartov T. Ryberg O. Ritter 《Geophysical Journal International》2007,170(2):737-748
Magnetotelluric and seismic methods provide complementary information about the resistivity and velocity structure of the subsurface on similar scales and resolutions. No global relation, however, exists between these parameters, and correlations are often valid for only a limited target area. Independently derived inverse models from these methods can be combined using a classification approach to map geologic structure. The method employed is based solely on the statistical correlation of physical properties in a joint parameter space and is independent of theoretical or empirical relations linking electrical and seismic parameters. Regions of high correlation (classes) between resistivity and velocity can in turn be mapped back and re-examined in depth section. The spatial distribution of these classes, and the boundaries between them, provide structural information not evident in the individual models. This method is applied to a 10 km long profile crossing the Dead Sea Transform in Jordan. Several prominent classes are identified with specific lithologies in accordance with local geology. An abrupt change in lithology across the fault, together with vertical uplift of the basement suggest the fault is sub-vertical within the upper crust. 相似文献
994.
Young Hong Shin Houze Xu Carla Braitenberg Jian Fang Yong Wang 《Geophysical Journal International》2007,170(3):971-985
995.
996.
A multifold crustal-scale deep seismic near-vertical reflection profile generates a large number of single-ended shot gathers, which provide redundant data sets because of overlapping coverage of the shallow refractors. We present an approach for deriving the shallow velocity structure by modelling and inversion of single-ended seismic refraction first arrival traveltime data. We apply this method to a data set acquired with a 12-km long spread with 100 m spacing of shots and receivers, of the Neoproterozoic Marwar basin in the NW Indian shield. The approach is shown to be quite successful for delineating the shallow refractor depths, steep dips and velocities, even in the absence of regular reverse refraction profiles. The study reveals two-layered sedimentary formations, Malani volcanics and a complicated basement configuration of the Marwar basin, and provides a measure of resolution and uncertainty of the estimated model parameters. A seismic section of the near-trace gather is found to be qualitatively consistent with the derived structural features of the basin. The relative highs and lows, observed in the Bouguer gravity profile, further corroborate the derived velocity model. The present approach can be especially useful in offshore areas and elsewhere, where the single-ended multifold seismic profiles are the only available data sets. 相似文献
997.
Jong-Chan Park Woohan Kim Tae Woong Chung Chang-Eob Baag Jin-Han Ree 《Geophysical Journal International》2007,169(3):1103-1114
We evaluate the stress field in and around the southern Korean Peninsula with focal mechanism solutions, using the data collected from 71 earthquakes ( ML = 1.9–5.2) between 1999 and 2004. For this, the hypocentres were relocated and well-constrained fault plane solutions were obtained from the data set of 1270 clear P -wave polarities and 46 SH / P amplitude ratios. The focal mechanism solutions indicate that the prevailing faulting types in South Korea are strike-slip-dominant-oblique-slip faultings with minor reverse-slip component. The maximum principal stresses (σ1 ) estimated from fault-slip inversion analysis of the focal mechanism solutions show a similar orientation with E–W trend (269°–275°) and low-angle plunge (10°–25°) for all tectonic provinces in South Korea, consistent with the E–W trending maximum horizontal stress (σHmax ) of the Amurian microplate reported from in situ stress measurements and earthquake focal mechanisms. The directions of the intermediate (σ2 ) and minimum (σ3 ) principal stresses of the Gyeongsang Basin are, however, about 90 deg off from those of the other tectonic provinces on a common σ2 –σ3 plane, suggesting a permutation of σ2 and σ3 . Our results incorporated with those from the kinematic studies of the Quaternary faults imply that NNW- to NE-striking faults (dextral strike-slip or oblique-slip with a reverse-slip component) are highly likely to generate earthquakes in South Korea. 相似文献
998.
1997年11月8日西藏Mw7.5级玛尼地震是干涉雷达技术应用于地震观测以来的一次重要事件.在第一部分中,我们应用广泛使用的Okada线弹性位错模型,假设断层的各个分段滑动量均匀,反演得到断层各个分段的几何参数和均匀滑动量.本部分的反演进一步去除滑动均匀假设,并利用更能反映断层真实状态的角形元位错模型(线弹性),在第一部分反演得到断层几何的基础上,反演断层面的静态位错分布.反演结果表明,线弹性滑动分布模型能够更好地解释观测数据,进一步提高反演的数据拟合程度.最终得到了断层面上的走滑和倾滑位错分布.首次得到的断层面滑动分布显示断层面滑动在浅部(0~12 km)比较集中,地震破裂长度约170 km,最大左旋走滑位移达4.8 m;反演结果还表明局部段落存在较大倾滑位移,量值达到1.9 m,这在断层模型中是不能忽略的,它可能是断层两侧形变不对称的原因之一;反演得到的标量地震矩为2.18×1020 N·m,相当于矩震级Mw7.5,与Velasco等利用地震波形反演得到的结果一致. 相似文献
999.
Twenty broadband seismographs were deployed along Hongyuan, Sichuan to Wuwei, Gansu. 81 teleseismic events were recorded in one year. We computed receiver functions from teleseismic waveform data and obtained S wave velocity structure beneath each station along the profile by using receiver function inversion method. The results revealed that the crustal structure is very complex and crustal average S wave velocity is to be on the low side. Low velocity structure generally exists in the depth range of 10~40 km in the crust between Aba arc fault and northern edge fault of Qinling earth's axis and it is a tectonic feature of complex geological process such as ancient A'nyemaqen Tethys ocean from closing and side colliding to subducted plate exhumed or thrust rock slice lifted. The Moho is about 50 km depth along the profile and is slightly deeper in the south than in the north. 相似文献
1000.
Automatic Interpretation of Magnetic Data Using Euler Deconvolution with Nonlinear Background 总被引:1,自引:0,他引:1
Pawan Dewangan T. Ramprasad M. V. Ramana M. Desa B. Shailaja 《Pure and Applied Geophysics》2007,164(11):2359-2372
The voluminous gravity and magnetic data sets demand automatic interpretation techniques like Naudy, Euler and Werner deconvolution.
Of these techniques, the Euler deconvolution has become a popular choice because the method assumes no particular geological
model. However, the conventional approach to solving Euler equation requires tentative values of the structural index preventing
it from being fully automatic and assumes a constant background that can be easily violated if the singular points are close
to each other. We propose a possible solution to these problems by simultaneously estimating the source location, depth and
structural index assuming nonlinear background. The Euler equation is solved in a nonlinear fashion using the optimization
technique like conjugate gradient. This technique is applied to a published synthetic data set where the magnetic anomalies
were modeled for a complex assemblage of simple magnetic bodies. The results for close by singular points are superior to
those obtained by assuming linear background. We also applied the technique to a magnetic data set collected along the western
continental margin of India. The results are in agreement with the regional magnetic interpretation and the bathymetric expressions. 相似文献