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61.
依托“西部煤炭资源高精度三维地震勘探技术”工程,对晋城矿区进行了旨在提高小断层,小陷落柱探测能力的高密度三维地震勘探。根据面元选择因素及该区地质任务,采用5m×5m网格进行野外数据采集;考虑炮检距、方位角、覆盖次数、排列片横纵比及煤层埋深(350~500m)等因素,采用中点放炮、60道接收,24次覆盖(横向4次,纵向6次)的8线16炮束状观测系统,基岩中激发。原始资料经同一处理流程后,获得5m×5m×1ms、5m×10m×1ms、10m×10m×1ms及2.5m×2.5m×1ms不同单元的三维数据体多个,通过对比可以发现小断层,小陷落柱在其小面元叠加时间剖面、顺层切片及相干切片都有清晰的反映。实例说明,小面元采集技术可以提高对小构造的纵、横向分辨能力,满足山区对三维地震精确勘探的要求。 相似文献
62.
屯兰矿南五采区地形复杂,最大高差达271m,地表大面积为第四系黄土覆盖,激发困难。为探索研究小面元三维地震勘探技术的应用效果。在常规三维地震勘区域内划出1km^2,采用5m×5m小面元进行采集。在地震数据采集过程中,采取了加大激发井深、提高覆盖次数、减小CMP面元网格和加大接收排列等技术措施,做到“四小三高、二中一深、两个等高面”。通过插值、抽线及扩大面元处理。获得2.5m×2.5m×1ms、5m×5m×1ms、5m×10m×1ms、10m×10m×1ms以及不同叠加次数的三维数据体。资料解释工作主要是在5m×5m×1ms、2.5m×2.5m×1ms两个数据体上进行,解释落差大于或等于5m的断层6条,落差3~5m的断层8条;查明长轴直径20~30m的陷落柱4个。30~100m的陷落柱1个,大于100m的陷落柱3个。与相邻区常规三维地震比较,小面元三维地震勘探有利于对小陷落柱、小断层的控制和解释。 相似文献
63.
龙固井田为全隐蔽的华北型煤田,位于巨野煤田中部,其首采扩大区主采煤层为3号煤层。考虑3煤层顶板稳定性主要受其顶板的构造信息和岩性信息影响,因此首先依据三维地震勘探综合解释成果及波阻抗反演解释成果对二者进行定量化,然后对波阻抗数据进行归一化处理,使得波阻抗数据和量化后的构造数据具有相同的变化范围及等量贡献。在此距离范围内构造和岩性的权值各为0.5,依此生成综合因素煤层顶板稳定性隶属度。分析3煤层顶板以上10m、20m处的综合因素煤层顶板稳定性隶属度图可以发现,该区3煤层顶板稳定性比较好。且其稳定性主要是受构造因素控制,岩性因素相对影响较小。 相似文献
64.
成矿理论与勘探实践证明,东部一些老矿由于勘探深度、范围的限制以及认识上的局限,在矿区深部、周边仍有一些矿未能发现和查明,其中相当一部分仍具有找矿潜力;而寻找西部新的煤炭资源是国家“稳定东部发展西部”战略需要。针对中国东西部不同的地质条件和勘探目标,其地震勘探野外施工方法及资料处理原则有所差异;而资料解释在东部以查明地层赋存形态、煤层赋存范围、构造发育特征为主,西部则以寻找煤系地层波阻抗差异明显、连续性好的反射波组为解释重点。地震勘探技术在中国东西部的二个典型地震时间剖面佐证了其在深部找矿的应用效果。 相似文献
65.
在山区或地表复杂地区进行地震勘探,采用基于地表一致性假设的静校正将会严重影响勘探效果,该影响主要源于地表一致性假设存在着不合理因素。如较高的低速带、巨厚的低速带、基岩裸露、地形起伏较大等。为分析一致性假设静校正偏差产生的原因及大小.构建一地形起伏、基岩出露的复杂模型,通过正演其射线路径,对比其时距曲线与理论时距曲线的差异,以及二者静校正量误差大小。模型分析证实该差异与偏移距、地震波穿透深度及基准面高程之间存在直接的联系,据此提出了改进方法,如浮动基准面校正及分块静校正等。理论模型和实际地震资料试算表明,使用改进的方法可有效改善地震时间刮面同相轴聚焦效果及连续性。 相似文献
66.
Yu. A. Kugaenko V. A. Saltykov V. I. Sinitsyn A. A. Shishkin 《Russian Journal of Pacific Geology》2008,2(3):218-227
In 2003–2004, long-term seismic noise observations were launched on Shikotan Island (Lesser Kuril Range) based on the “Shikotan” dormant regional seismic station. The geological and geophysical data on the registration area are reported. Information about the equipment and its technical specifications is given. The precursors to the strongest local earthquakesthat occurred in the Shikotan Island region in January 2005–March 2007 are identified. 相似文献
67.
We estimate (/T)
P
of the lower mantle at seismic frequencies using two distinct approaches by combining ambient laboratory measurements on lower mantle minerals with seismic data. In the first approach, an upper bound is estimated for |(/T)
P
| by comparing the shear modulus () profile of PREM with laboratory room-temperature data of extrapolated to high pressures. The second approach employs a seismic tomography constraint ( lnV
S
/ lnV
P
)
P
=1.8–2, which directly relates (/T)
P
with (K
S
/T)
P
. An average (K
S
/T)
P
can be obtained by comparing the well-established room-temperature compression data for lower mantle minerals with theK
S
profile of PREM along several possible adiabats. Both (K
S
/T) and (/T) depend on silicon content [or (Mg+Fe)/Sil of the model. For various compositions, the two approaches predict rather distinct (/T)
P
vs. (K
S
/T)
P
curves, which intersect at a composition similar to pyrolite with (/T)
P
=–0.02 to –0.035 and (K
S
/T)
P
=–0.015 to –0.020 GPa/K. The pure perovskite model, on the other hand, yields grossly inconsistent results using the two approaches. We conclude that both vertical and lateral variations in seismic velocities are consistent with variation due to pressure, temperature, and phase transformations of a uniform composition. Additional physical properties of a pyrolite lower mantle are further predicted. Lateral temperature variations are predicted to be about 100–250 K, and the ratio of ( lnp/ lnV
S
)
P
around 0.13 and 0.26. All of these parameters increase slightly with depth if the ratio of ( lnV
S
/ lnV
P
)
P
remains constant throughout the lower mantle. These predicted values are in excellent agreement with geodynamic analyses, in which the ratios ( ln / lnV
S
)
P
and ( / lnV
S
)
P
are free parameters arbitrarily adjusted to fit the tomography and geoid data. 相似文献
68.
通过对北京遥测地震台网近年来记录到的北京及邻区地震的震中分布,地震活动频度及能量释放强度的分析,得到本区地震活动在时间分布上具有“聚堆性”。在年发震频度,地震强度和能释放方面均具有双峰值特征,并且具有较好的一致性和同步性,在空间分布上具有条带特征,且形成北东~南西和北西~南东的两条相互交汇的条带。又通过统计分析得到本区发震概率最大的时间段是每年的10月前后,而地震主要发生在北西~南东带上。 相似文献
69.
Erik Rüttener Juan José Egozcue Dieter Mayer-Rosa Stephan Mueller 《Natural Hazards》1996,14(2-3):165-178
Seismic hazard analysis is based on data and models, which both are imprecise and uncertain. Especially the interpretation of historical information into earthquake parameters, e.g. earthquake size and location, yields ambiguous and imprecise data. Models based on probability distributions have been developed in order to quantify and represent these uncertainties. Nevertheless, the majority of the procedures applied in seismic hazard assessment do not take into account these uncertainties, nor do they show the variance of the results. Therefore, a procedure based on Bayesian statistics was developed to estimate return periods for different ground motion intensities (MSK scale).Bayesian techniques provide a mathematical model to estimate the distribution of random variables in presence of uncertainties. The developed method estimates the probability distribution of the number of occurrences in a Poisson process described by the parameter . The input data are the historical occurrences of intensities for a particular site, represented by a discrete probability distribution for each earthquake. The calculation of these historical occurrences requires a careful preparation of all input parameters, i.e. a modelling of their uncertainties. The obtained results show that the variance of the recurrence rate is smaller in regions with higher seismic activity than in less active regions. It can also be demonstrated that long return periods cannot be estimated with confidence, because the time period of observation is too short. This indicates that the long return periods obtained by seismic source methods only reflects the delineated seismic sources and the chosen earthquake size distribution law. 相似文献
70.
A. McGarr 《Pure and Applied Geophysics》1994,142(3-4):467-489
Although laboratory stick-slip friction experiments have long been regarded as analogs to natural crustal earthquakes, the potential use of laboratory results for understanding the earthquake source mechanism has not been fully exploited because of essential difficulties in relating seismographic data to measurements made in the controlled laboratory environment. Mining-induced earthquakes, however, provide a means of calibrating the seismic data in terms of laboratory results because, in contrast to natural earthquakes, the causative forces as well as the hypocentral conditions are known. A comparison of stick-slip friction events in a large granite sample with mining-induced earthquakes in South Africa and Canada indicates both similarities and differences between the two phenomena. The physics of unstable fault slip appears to be largely the same for both types of events. For example, both laboratory and mining-induced earthquakes have very low seismic efficiencies
where
a
is the apparent stress and
is the average stress acting on the fault plane to cause slip; nearly all of the energy released by faulting is consumed in overcoming friction. In more detail, the mining-induced earthquakes differ from the laboratory events in the behavior of as a function of seismic momentM
0. Whereas for the laboratory events 0.06 independent ofM
0, depends quite strongly onM
0 for each set of induced earthquakes, with 0.06 serving, apparently, as an upper bound. It seems most likely that this observed scaling difference is due to variations in slip distribution over the fault plane. In the laboratory, a stick-slip event entails homogeneous slip over a fault of fixed area. For each set of induced earthquakes, the fault area appears to be approximately fixed but the slip is inhomogeneous due presumably to barriers (zones of no slip) distributed over the fault plane; at constant
, larger events correspond to larger
a
as a consequence of fewer barriers to slip. If the inequality
a
/
0.06 has general validity, then measurements of
a
=µE
a
/M
0, where is the modulus of rigidity andE
a
is the seismically-radiated energy, can be used to infer the absolute level of deviatoric stress at the hypocenter. 相似文献