潮汐触发地震研究进展综述   总被引：3，自引：0，他引：3  

李金  蒋海昆 《地震》2011,31(4):36-47

对近年来国内外潮汐调制触发地震研究进行了系统综述。 介绍了月相与地震活动的关系, 日月引潮力及其分量对地震触发的情况, 基于大样本统计的潮汐触发地震研究等内容。 月相与地震活动的简单对应是对潮汐触发地震的初步研究, 调制比是对这一现象的定量化描述。 潮汐应力分解及对地震活动影响的研究, 则是从力学的层面揭示两者之间的可能关系。 大样本统计则从统计的角度研究潮汐对地震的关系, 众多统计方法中应用较多的是Schuster检验, 它将震源机制、 潮汐应力、 统计检验等因素综合考虑, 定量地分析潮汐对地震的触发作用。  相似文献   

Morphological responses of an estuarine intertidal mudflat to constructions since 1978 to 2005: The Seine estuary (France)     

Antoine Cuvilliez  Julien Deloffre  Robert Lafite  Christophe Bessineton 《Geomorphology》2009,104(3-4):165-174

Since 1834 the Seine estuary (France) has been the site of numerous construction projects with the aim to accommodate and secure boat traffic. Since 1978, the increasing of the activities of Le Havre port, located at the mouth of the estuary, has accelerated the construction work rate. Several dykes, a bridge, and new port facilities have been constructed in rapid succession, modifying considerably the hydrodynamic conditions which sustain a partially vegetated sandy–muddy tidal flat located in the North bank of the estuary between the new port of Le Havre and the Normandy bridge achieved in 1995.The present study deals with the morphological evolution of this zone from 1978 to 2005. The use of a low altitude remote sensing technique combined with traditional methods of ground survey and probes allow to demonstrate the impact of human activities on sedimentary and vegetation dynamics. The Northern mudflat of the estuary is the most affected by these human activities, which surface have reduced of 62% during the last 27 years with an intensified local erosion during the last 27 months corresponding to a loss 1 250 000 m³ of fine-grained sediment. At the same time, the general sanding up in the channel of the zone has caused a loss of more than 31% of the tidal prism, more than three quarters of which occurred during the last three years. Results also establish that the response times of the sedimentary or topographic readjustment to an installation depend on the extent and the nature of the construction. In fact, the sedimentary readjustments to an installation can be delayed by up to 10 years in the case of the Seine estuary. This delay is explained by a rapid succession of construction works which may occult the effect of a single installation. Except in the case of a dyke built perpendicular to ebb and flood currents, the impacts of these installations reach a hydro-sedimentary equilibrium on the level between 1 and 7 years after their completion.  相似文献   

1973~1976年四川松潘强震序列的应力触发过程   总被引：13，自引：6，他引：7       下载免费PDF全文

朱航  闻学泽 《地球物理学报》2009,52(4):994-1003

本文计算和研究了1973~1976年四川松潘4次强震组成的序列引起的库仑应力变化图像,分析了由该序列各次事件引起的近场应力变化及其与后续强震发生以及余震分布的关系,同时分析了该序列引起的远场应力变化与随后25年区域中-强地震活动的关系.结果显示：1973年8月11日松潘黄龙6.5级地震导致虎牙断裂带中段上库仑应力的显著增加并触发了1976年8月16日的7.2级地震;此后,又沿断层向南相继触发了1976年8月22日的6.7级地震和8月23日的7.2级地震.该序列的绝大多数余震主要发生在主震发震断层的近场库仑应力增加区.另外,在该强震序列发生后的25年中、在距该序列发震断层中部约200 km范围内,6次5.0~6.6级地震均发生在由该序列引起的远场、微量的库仑应力变化增加区中.  相似文献   

断-块模型中走滑型地震应力触发研究——以青藏高原北部几次强震为例   总被引：1，自引：0，他引：1       下载免费PDF全文

王凯英 《地球物理学报》2009,52(7):1776-1781

从发震断层与活动块体的分布关系出发,以青藏高原北部地区几次强震为例,研究了介质非连续的断－块构造模型中地震永久位移造成的区域断层静库仑应力变化．研究表明,在断块构造模型中,走滑型为主的地震位错引起的区域断层库仑应力变化在地震破裂面以外随距离衰减很快,影响范围仅为几十公里,和余震分布尺度相当;对有地表破裂数据的1937年M7.5花石峡地震、1997年M7.5玛尼地震和2001年M7.8可可西里地震的模拟结果显示,先前地震的断层位移在后续地震断层面所造成的库仑应力甚微,预示了远距离地震之间的静应力触发效应不明显．  相似文献   

Numerical study of three-dimensional shelf circulation on the Scotian Shelf using a shelf circulation model     

Kyoko Ohashi  Jinyu Sheng  Keith R. Thompson  Charles G. Hannah  Harold Ritchie 《Continental Shelf Research》2009

A numerical shelf circulation model was developed for the Scotian Shelf, using a nested-grid setup consisting of a three-dimensional baroclinic inner model embedded inside a two-dimensional barotropic outer model. The shelf circulation model is based on the Princeton Ocean Model and driven by three-hourly atmospheric forcing provided by a numerical weather forecast model and by tidal forcing specified at the inner model's open boundaries based on pre-calculated tidal harmonic constants. The outer model simulates the depth-mean circulation forced by wind and atmospheric pressure fields over the northwest Atlantic Ocean with a horizontal resolution of 1/12°. The inner model simulates the three-dimensional circulation over the Gulf of St. Lawrence, the Scotian Shelf, and the adjacent slope with a horizontal resolution of 1/16°. The performance of the shelf circulation model is assessed by comparing model results with oceanographic observations made along the Atlantic coast of Nova Scotia and in the vicinity of Sable Island (on the Scotian Shelf) during two periods: October 2000–March 2001 and April–June 2002. Analysis of model results on Sable Island Bank indicates that tidal currents account for as much as ∼80% of the total variance of near-bottom currents, and currents driven by local winds account for ∼30% of the variance of the non-tidal near-bottom currents. Shelf waves generated remotely by winds and propagating into the region also play an important role in the near-bottom circulation on the bank.  相似文献   

Analytical study of the transverse distribution of along-channel and transverse residual flows in tidal estuaries   总被引：2，自引：0，他引：2  

K.M.H. Huijts  H.M. Schuttelaars  H.E. de Swart  C.T. Friedrichs 《Continental Shelf Research》2009

We present an analytical model to decompose complex along-channel and transverse residual flows into components induced by individual mechanisms. The model describes the transverse distribution of residual flows in tidally dominated estuaries. Scaling and perturbation techniques are used to obtain analytical solutions for residual flows over arbitrary across-channel bed profiles. The flows are induced by horizontal density gradients, tidal rectification processes, river discharge, wind, channel curvature and the earth's rotation. These rectification processes induce residual flows that are up-estuary to the right and down-estuary to the left of an estuarine channel (looking up-estuary in the northern hemisphere). The tidal rectification processes fundamentally change the transverse structure of along-channel residual flows in many tidal estuaries, as these processes cause the flows to be internally asymmetric about the mid-axis of the channel for relatively large tidal velocities, steep channels or narrow estuaries. In addition, velocity scales are derived from the analytical solutions to estimate the relative importance of the various residual flow mechanisms from estuarine parameters. A case study of a transect across the Upper Chesapeake Bay showed that important features of the residual flow observed in that transect are reproduced and explained by the analytical model. The velocity scales were able to identify the relevant residual flow mechanisms as well. The tidal rectification processes considered here result from advection of along-channel tidal momentum by Coriolis-induced transverse tidal currents.  相似文献   

SST observations of upwelling induced by tidal straining in the Rhine ROFI     

Gerben J. de Boer  Julie D. Pietrzak  Johan C. Winterwerp 《Continental Shelf Research》2009

In this paper SST imagery and a three-dimensional numerical model of a river plume were employed to detect upwelling induced by tidal straining in the Rhine ROFI (region of fresh water influence). Previous studies have shown that the Rhine ROFI in the North Sea exhibits strong cross-shore density gradients that compete with tidal and wind mixing to establish stratification. During neap periods with low mixing energy an area measuring 30 km offshore by 100 km alongshore becomes stratified. When the ROFI is stratified strong cross-shore currents are observed, with surface currents rotating anti-cyclonically and bottom currents rotating cyclonically. The cross-shore currents interact with the cross-shore density gradients to produce a semi-diurnal cycle of stratification. Due to continuity requirements imposed by the proximity of the coast, the offshore-directed surface currents and onshore-directed bottom currents should lead to coastal upwelling.  相似文献   

观测井深度与井水位地震监测效能的关系     

张敏 《高原地震》2009,21(4):9-13

从井水位固体潮汐响应及同震响应等方面系统研究了不同观测含水层中观测井的深度对地震监测效能的影响问题,并讨论了影响监测能力的其他因素,提出了理想的观测井深度。  相似文献   

Stress changes on major faults caused by <Emphasis Type="Italic">M</Emphasis><Subscript>w</Subscript>7.9 Wenchuan earthquake,May 12, 2008     

Bin Shan  Xiong Xiong  Yong Zheng  FaQi Diao 《中国科学D辑(英文版)》2009,52(5):593-601

On May 12, 2008, a magnitude 7.9 earthquake ruptured the Longmenshan fault system in Sichuan Province, China, collapsing buildings and killing tens of thousands people. As predicted, aftershocks may last for at least one year, and moreover, large aftershocks are likely to occur. Therefore, it is critical to outline the areas with potential aftershocks before reconstruction and re-settling people as to avoid future disasters. It is demonstrated that the redistribution of stress induced by an earthquake should trigger successive seismic activity. Based on static stress triggering theory, we calculated the coseismic stress changes on major faults induced by the Wenchuan earthquake, with elastic dislocation theory and the multilayered crustal model. We also discuss the stress distribution and its significance for future seismic activity under the impact of the Wenchuan earthquake. It is shown that coulomb failure stress (CFS) increases obviously on the Daofu-Kangding segment of the Xianshuihe Fault, the Maqu and Nanping segment of the Eastern Kunlun Fault, the Qingchuan Fault, southern segment of the Minjiang Fault, Pengxian-Guanxian Fault, Jiangyou-Guangyuan Fault, and Jiangyou-Guanxian Fault. The increased stress raises the probability of earthquake occurrence on these faults. Since these areas are highly populated, earthquake monitoring and early disaster alarm system are needed. CFS increases with a magnitude of 0.03–0.06 MPa on the Qingchuan Fault, which is close to the northern end of the rapture of Wenchuan earthquake. The occurrence of some strong aftershocks, including three events with magnitude higher than 5.0, indicates that the seismic activities have been triggered by the main shock. Aftershocks seem to migrate northwards. Since the CFS change on the Lueyang-Mianxian Fault located on the NEE of the Qingchuan Fault is rather small (±0.01 MPa), the migration of aftershocks might be terminated in the area near Hanzhong City. The CFS change on the western Qinling Fault is around 10 Pa, and the impact of static triggering can be neglected. The increment of CFS on the Pengxian-Guanxian Fault and Beichuan-Yingxiu Fault southwest to the main rupture is 0.005–0.015 MPa, which would facilitate earthquake triggering in these areas. Very few aftershocks in these areas indicate that the accumulated stress has not been released sufficiently. High seismic risk is predicated in these areas due to co-seismic CFS loading. The Wenchuan earthquake released the accumulated CFS on the Fubianhe Fault, the Huya Fault, the Ha’nan-Qingshanwan Fault, and the Diebu-Bailongjiang Fault. The decrement of CFS changes on the Longquanshan Fault east to Chengdu City is about 0.002 MPa. The seismic activity will be depressed by decrement of CFS on these faults. Supported by Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. KZCX-SW-153), National Natural Science Foundation of China (Grant Nos. 40574011 and 40474028)  相似文献   

Suspended sediment transport in the German Wadden Sea—seasonal variations and extreme events     

Alexander Bartholomä  Adam Kubicki  Thomas H. Badewien  Burghard W. Flemming 《Ocean Dynamics》2009,59(2):213-225

The German Wadden Sea (southern North Sea) sediments are composed of both cohesive and non-cohesive deposits. The spatial distribution patterns are mainly driven by wind-induced waves and tidal currents. Transport intensity and duration depend on the hydrodynamic conditions, which vary over time. In this paper, the transport of suspended sediment was investigated on seasonal, tidal and hourly time scales in the back-barrier system of Spiekeroog Island. Long- and short-term data of fair weather periods and two storm events were investigated based on stationary and mobile measurements of currents and waves by Acoustic Doppler Current Profiler (ADCP), in situ particle size and suspended sediment concentration (SSC) measurements by laser in situ scattering and transmissometry (LISST) as well as wind records. The ADCP backscatter intensities were calibrated by means of LISST volume concentration data in order to quantify longer term SSCs and fluxes in the back-barrier system. Values up to 120 mg l⁻¹ were recorded, but concentrations more commonly were below 60 mg l⁻¹. The long-term results confirm former observations of a balanced budget during low-energy (fair weather) conditions in the study area. In general, SSCs were higher during spring tides than during neap tides. The data also clearly show the remobilisation of sediment by tidal current entrainment. The records include two severe storm events, “Britta” (1st November 2006) and “Kyrill” (18th January 2007). The data reveal very complex temporal flow and transport patterns. During both storm events, the export of material was mainly controlled by the interaction of wind, waves and tidal phase. The typical ebb-dominance occurring during fair-weather conditions was temporarily neutralised and even reversed to a flood-dominated situation. During “Kyrill”, the wind and high-waves setup in conjunction with the tidal phase was even able to compress the duration of two successive ebb cycles by over 70%. Although SSCs increased during both storms and higher turbulence lifted particle clouds upwards, an export of suspended matter towards the North Sea was only observed under the conditions taking place during “Britta”. Such fluxes, however, are currently still difficult to quantify because the backscatter intensity during high energy events includes a substantial amount of noise produced by the high turbulence, especially near the water surface.  相似文献