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931.
932.
堤防隐患探测实例分析 总被引:2,自引:0,他引:2
在堤防隐患探测中,采用地质雷达、高密度电法、电测深法、地震折射波法等综合物探技术,并结合少量的土工试验资料,提高了物探成果的可靠性和实用性,取得了良好的应用效果.为堤防隐患探测提供了新的思路。 相似文献
933.
934.
935.
西昆仑以其强烈的构造变形、频繁的岩浆活动、漫长的地质演化历史及特殊的大地构造环境而具有得天独厚的成矿地质条件。然而由于恶劣的自然地理条件所限,该区地质矿产工作程度一直较低。2002~2003年度,作者在野外调查过程中,在麻扎东陆续发现了三处五个以铜为主的多金属矿(化)体。它们与康西瓦—苏巴什构造带在空间、时间和成因上有着密切的依存关系,构成黑恰达坂多金属矿化带。虽然带内矿体品位较低,但规模巨大,具有较好的成矿地质条件和明显的化探异常显示,找矿前景良好。 相似文献
936.
Annabel Kelly Richard W. England Peter K. H. Maguire 《Geophysical Journal International》2007,171(3):1172-1184
A regional model of the 3-D variation in seismic P -wave velocity structure in the crust of NW Europe has been compiled from wide-angle reflection/refraction profiles. Along each 2-D profile a velocity–depth function has been digitised at 5 km intervals. These 1-D velocity functions were mapped into three dimensions using ordinary kriging with weights determined to minimise the difference between digitised and interpolated values. An analysis of variograms of the digitised data suggested a radial isotropic weighting scheme was most appropriate. Horizontal dimensions of the model cells are optimised at 40 × 40 km and the vertical dimension at 1 km. The resulting model provides a higher resolution image of the 3-D variation in seismic velocity structure of the UK, Ireland and surrounding areas than existing models. The construction of the model through kriging allows the uncertainty in the velocity structure to be assessed. This uncertainty indicates the high density of data required to confidently interpolate the crustal velocity structure, and shows that for this region the velocity is poorly constrained for large areas away from the input data. 相似文献
937.
938.
High-resolution structures of the Landers fault zone inferred from aftershock waveform data 总被引:2,自引:0,他引:2
High-frequency body waves recorded by a temporary seismic array across the surface rupture trace of the 1992 Landers, California, earthquake were used to determine fault-zone structures down to the seismogenic depth. We first developed a technique to use generalized ray theory to compute synthetic seismograms for arbitrarily oriented tabular low-velocity fault-zone models. We then generated synthetic waveform record sections of a linear array across a vertical fault zone. They show that both arrival times and waveforms of P and S waves vary systematically across the fault due to transmissions and reflections from boundaries of the low-velocity fault zone. The waveform characteristics and arrival-time patterns in the record sections allow us to locate the boundaries of the fault zone and to determine its P - and S -wave velocities independently as well as its depth extent. Therefore, the trade-off between the fault-zone width and velocities can be avoided. Applying the method to the Landers waveform data reveals a low-velocity zone with a width of 270–360 m and a 35–60 per cent reduction in P and S velocities relative to the host rock. The analysis suggests that the low-velocity zone extends to a depth of ∼7 km. The western boundary of the low-velocity zone coincides with the observed main surface rupture trace. 相似文献
939.
结合安徽省高速公路建设工程实例,介绍瞬态瑞雷面波勘探技术在公路工程地质勘察中的应用,解决沿线高边坡、深路堑、桥梁、隧道进出口的岩土分层,给出基岩风化分带等工程地质问题,省时、省力,取得了良好的经济效益和环境效益. 相似文献
940.
Urban Seismic Risk Evaluation: A Holistic Approach 总被引:3,自引:4,他引:3
Risk has been defined, for management purposes, as the potential economic, social and environmental consequences of hazardous
events that may occur in a specified period of time. However, in the past, the concept of risk has been defined in a fragmentary
way in many cases, according to each scientific discipline involved in its appraisal. From the perspective of this article,
risk requires a multidisciplinary evaluation that takes into account not only the expected physical damage, the number and
type of casualties or economic losses, but also the conditions related to social fragility and lack of resilience conditions,
which favour the second order effects (indirect effects) when a hazard event strikes an urban centre. The proposed general
method of urban risk evaluation is multi hazard and holistic, that is, an integrated and comprehensive approach to guide decision-making.
The evaluation of the potential physical damage (hard approach) as the result of the convolution of hazard and physical vulnerability
of buildings and infrastructure is the first step of this method. Subsequently, a set of social context conditions that aggravate
the physical effects are also considered (soft approach). In the method here proposed, the holistic risk evaluation is based
on urban risk indicators. According to this procedure, a physical risk index is obtained, for each unit of analysis, from
existing loss scenarios, whereas the total risk index is obtained by factoring the former index by an impact factor or aggravating
coefficient, based on variables associated with the socio-economic conditions of each unit of analysis. Finally, the proposed
method is applied in its single hazard form to the holistic seismic risk evaluation for the cities of Bogota (Colombia) and
Barcelona (Spain). 相似文献