常Q滞弹性介质地震波动数值模拟——时域本构优化逼近          下载免费PDF全文

谢志南  郑永路  章旭斌 《地球物理学报》2018,61(10):4007-4020

在地震波动模拟中计入常Q滞弹性阻尼，可有效降低模拟波形的误差.就时域有限差分和有限元模拟而言，常基于广义标准线性体建立阻尼介质的时域本构逼近.广义标准线性体由若干标准线性体并联得到，增加标准线性体个数能有效提高模拟精度，但计算量及计算存储将成倍增长.目前尚未有普适的标准线性体个数优化取值方案.本文基于广义标准线性体参数的非线性优化拟合方法，详细分析了时域本构逼近误差的影响因素，清楚揭示了逼近误差仅取决于频带宽度，与频带上下限取值无关这一特性，阐明了构建具有普适性标准线性体个数优化取值方案的可行性.论证了波形模拟精度主要取决于波传播距离与模拟波长的比值以及标准线性体的个数取值.综合考虑上述两个控制因素，结合在波动正反演问题中广为采纳的波形时频误差衡量准则，对不同Q值介质给出了标准线性体个数优化取值表.进一步，本文提出采用不同个数标准线性体以近似不同Q值的阻尼介质时域本构，解决了以往波动数值模拟中统一采用相同个数标准线性体而导致的计算量及计算存储浪费或模拟精度低下等问题，并基于数值实验验证了这一方法的精度.本文工作对推进滞弹性介质波动数值模拟及其在全波形反演问题中的应用具有理论价值和实践意义.  相似文献   

华南陆缘高热流区的壳幔温度结构与动力学背景          下载免费PDF全文

张健  王蓓羽  唐显春  董淼  艾依飞 《地球物理学报》2018,61(10):3917-3932

华南陆缘是我国重要的矿产、地热资源区.晚中生代以来，在太平洋板块西向俯冲，地幔热对流活动共同作用下，该区出现多期岩浆-热事件和大规模爆发式成矿作用.在前人研究基础上，本文利用地表热流观测资料、地震剪切波资料、重力位球谐系数，计算了壳-幔温度结构，分析了动力学背景.计算结果表明：华南陆缘东南沿海地带，地壳10 km以浅温度达200℃以上，居里点温度475℃，莫霍面平均温度550℃.地壳浅层较热，花岗岩中放射性元素衰变放热是地壳浅层地下水热活动的重要热源，但地壳总体温度不高，为"冷壳热幔"型热结构.地幔中，90 km深度，温度950~1250℃；120 km深度，温度1050~1400℃；150 km深度，温度1200~1450℃；220 km深度，温度1500~1700℃."热"岩石圈底界深度在110~150 km之间，西深东浅.岩石圈内，地幔应力场为挤压-伸展相间格局；岩石圈之下，地幔应力场为一个以南昌为中心、长轴NE-SW向的椭圆.分析认为，晚中生代以来，太平洋板块的西向俯冲，导致华南陆缘在区域性SE向地幔对流背景上叠加局域性不稳定热扰动，在175~85Ma期间，上地幔物质向上流动，形成不同的岩浆活动高峰期.同时，岩石圈地幔受俯冲洋壳流体的影响，含水量高，黏度小，在地幔流切向应力场作用下，岩石圈底界由西向东"波浪"状减薄.现今岩石圈之下仍具备地幔小尺度热对流温度条件，但除地表浅层外，地壳整体温度不高，岩石圈构造稳定.  相似文献   

Conditional effects of tides and waves on short‐term marsh sedimentation dynamics          下载免费PDF全文

Zhigang Ma  Tom Ysebaert  Daphne van der Wal  Peter M.J. Herman 《地球表面变化过程与地形》2018,43(10):2243-2255

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3D P-WAVE VELOCITY STRUCTURE AT THE NORTHEASTERN MARGIN OF ORDOS BLOCK     

HAN Xiao-ming  Liu Fang  ZHANG Fan  CHEN Li-feng  LI Juan  LI Shuan-hu  YANG Hong-ying 《地震地质》2018,40(1):215-231

Using the 7 100 absolute first arrivals of P waves and 91 513 relative P arrival times of 726 events at the northeastern margin of the Ordos block since 2009, the 3D fine structure of P wave velocity within the depth of 15km in the crust was inverted by the double difference seismic tomography method. The results show that there exist obvious high-speed continuous bodies in the northwest of the study area, and their lateral areas increase gradually with depth, while the velocity of east and south is relatively low. The velocity inhomogeneity exists and differs at different depths. The lateral differences of velocity are related to seismicity and faults. The 5~15km depth profile shows that earthquakes tend to occur in the area with relatively high velocity or high speed transition zones, which to some extent reflects the fragility of regional crustal media and the strong differential movement of faults in vertical and horizontal directions where the crust body is easy to absorb and store strain energy and generate major earthquakes. A "Y"-shape low-velocity channel is present in the lower crust around Liangcheng, corresponding to the NW-trending Heilaoyao-Shahukou fault set, which may reveal the migration path of the Late Tertiary-Quaternary basalt eruption. The Helingeer M6.2 earthquake in 1976 was related to the formation of the locking section of the thermal welding in this area. The three-dimensional fine structure of P wave velocity presented in this paper provides intuitive seismological evidence for physical and chemical properties of crustal media and the deep tectonic environment of earthquake preparation.  相似文献   

Analysis of the Characteristics of the D.P.R. Korean Seismic Event on September 23, 2017     

Du Guangbao  Zhao Yong  Sun Li  He Shaolin  Liu Jie 《中国地震研究》2018,32(2):280-287

A M3. 4 seismic event occurred in the Punggye-ri nuclear test site,D. P. R Korea at 16∶29 p.m. on September 23,2017. We analyzed the waveforms of this event recorded by the China Earthquake Networks Center. In conclusion,this event is complex,including an explosion with a successive earthquake. Although the beginning of the event is an explosion,fault dislocation plays the main role in the event.  相似文献   

PS测井在机场隧道地基勘查中的应用          下载免费PDF全文

范伟顺 《山东国土资源》2018,34(1)

PS测井技术是地震勘探方法之一,也是一种简便、快速、准确的原位测试技术。该文介绍了单孔法PS测井的原理及其在铁路工程勘察中的应用,主要包括根据等效剪切波,进行建筑抗震场地类别划分,铁路工程抗震场地类别划分。根据岩土动力学参数,达到评价岩体质量和划分围岩类别目的,利用剪切波速法估算岩土的承载力基本值。通过青岛机场隧道场地的工程实例说明了PS测井技术在岩土工程勘察设计中的应用情况及应用效果。  相似文献   

1966—2018年河西走廊春季寒潮频次及影响因子分析          下载免费PDF全文

吕青松  辛存林  王瑞  张勃  张华 《干旱区地理》2020,43(4):946-954

基于甘肃河西走廊15个国家基准基本站点提供的1966年1月1日~2018年12月31日春季（3~5月）逐日最低气温值数据,利用线性回归分析方法、Spline空间插值法和Mann-Kendall趋势和突变检验法,探讨了河西走廊地区1966—2018年春季（3~5月）寒潮频次变化及其影响因子。研究表明：（1） 1966—2018年河西走廊地区春季（3~5月）单站寒潮频次总体呈现下降趋势〔–0.098次·（10 a）^–1〕,其中1980—2010年寒潮频次呈显著下降趋势,2010年之后下降趋势变缓,未通过显著性检验;区域寒潮53 a来频次总体呈缓慢下降趋势〔–0.015次·（10 a）^–1〕。（2） 近53 a河西走廊地区春季三个月中,单站寒潮总量4月>3月>5月,其中4月、5月寒潮频次下降不明显,3月频次下降显著。（3） 空间上,大致以北大河和黑河干流为界,两河中间区域春季寒潮频次低,而北大河以北和黑河干流以东区域则是寒潮高值区,走廊外围地区寒潮频次较高,且大多呈显著下降趋势,寒潮频次与气温距平存在明显负相关关系,内部地区变化趋势不明显。（4） 河西地区春季寒潮频次受气候变暖、地形和大气环流的影响,寒潮频次变化趋势存在地区差异。研究可提高对甘肃河西走廊寒潮演化过程的认知,为河西走廊气候变化的进一步研究奠定基础。  相似文献   

Source-independent wave-equation based microseismic source location using traveltime inversion          下载免费PDF全文

Songqin Nong  Chao Huang  Liangguo Dong 《地震科学（英文版）》2018,31(2):100-109

A new source location method using wave-equation based traveltime inversion is proposed to locate microseismic events accurately. With a sourceindependent strategy, microseismic events can be located independently regardless of the accuracy of the source signature and the origin time. The traveltime-residuals-based misfit function has robust performance when the velocity model is inaccurate. The new Fréchet derivatives of the misfit function with respect to source location are derived directly based on the acoustic wave equation, accounting for the influence of geometrical perturbation and spatial velocity variation. Unlike the mostly used traveltime inversion methods, no traveltime picking or ray tracing is needed.Additionally, the improved scattering-integral method is applied to reduce the computational cost. Numerical tests show the validity of the proposed method.  相似文献   

Full moment tensor inversion constrained by double-couple focal mechanism for induced seismicity*          下载免费PDF全文

Yuyang Tan  Haijiang Zhang  Junlun Li  Chen Yin  Furong Wu 《地震科学（英文版）》2020,33(4):177-193

In this study, we propose a new method to determine full moment tensor solution for induced seismicity. This method generalizes the full waveform matching algorithm we have developed to determine the double-couple (DC) focal mechanism based on the neighbourhood algorithm. One major difference between the new method and the former one is that we adopt a new misfit function to constrain the candidate moment tensor solutions with respect to a reference DC solution in addition to other misfit terms characterizing the waveform matching. Through synthetic tests using a real passive seismic survey geometry, the results show the new constraint can help better recover the DC components of inverted moment tensors. We further investigate how errors in the velocity model and source location affect the moment tensor solution. The synthetic test results indicate that the constrained inversion is robust in recovering both the DC and non-DC components. We also test the proposed method on several real induced events in an oil/gas field in Oman using the same observation system as synthetic tests. While it is found that the full moment tensor solutions without using the DC constraints have much larger non-DC components than solutions with the DC constraints, both solutions are able to fit the observed waveforms at similar levels. The synthetic and real test results suggest the proposed DC constrained inversion method can reliably retrieve full moment tensor solutions for the induced seismicity.  相似文献   

An interpretation of wave refraction and its influence on foreshore sediment distribution     

Joevivek Vincent Jayaraj  Chandrasekar Nainarpandian  Jayangondaperumal Ramakrishnan  Thakur Vikram Chandr  Shree Purniema Krishnan 《海洋学报(英文版)》2019,38(5):151-160

To analyze the grain size and depositional environment of the foreshore sediments, a study was undertaken on wave refraction along the wide sandy beaches of central Tamil Nadu coast. The nearshore waves approach the coast at 45° during the northeast(NE) monsoon, at 135° during the southwest(SW) monsoon and at 90° during the non-monsoon or fair-weather period with a predominant wave period of 8 and 10 s. A computer based wave refraction pattern is constructed to evaluate the trajectories of shoreward propagating waves along the coast in different seasons. The convergent wave rays during NE monsoon, leads to high energy wave condition which conveys a continuous erosion at foreshore region while divergent and inept condition of rays during the SW and non-monsoon, leads to moderate and less energy waves that clearly demarcates the rebuilt beach sediments through littoral sediment transport. The role of wave refraction in foreshore deposits was understood by grain size and depositional environment analysis. The presence of fine grains with the mixed population, during the NE monsoon reveals that the high energy wave condition and sediments were derived from beach and river environment. Conversely, the presence of medium grains with uniform population, during SW and non-monsoon attested less turbulence and sediments were derived from prolong propagation of onshore-offshore wave process.These upshots are apparently correlated with the in situ beach condition. On the whole, from this study it is understood that beaches underwent erosion during the NE monsoon and restored its original condition during the SW and non-monsoon seasons that exposed the stability of the beach and nearshore condition.  相似文献