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Microtremor
Microtremor is a low amplitude (in the order of micrometres) ambient vibration of the ground caused by man-made or atmospheric disturbances. The term Ambient Vibrations is now preferred to talk about this phenomenon. Observation of microtremors can give useful information on dynamic properties of the site such as predominant period and amplitude. Microtremor observations are easy to perform, inexpensive and can be applied to places with low seismicity as well, hence, microtremor measurements can be used conveniently for seismic microzonation.Nakamura, Y., 1989. A Method for Dynamic Characteristics Estimation of Subsurface Using Microtremor on the Ground Surface. Quarterly Report of RTRI, vol. 30, No. 1, pp. 25–33. More detailed information on the shear wave velocity profile of the site can be obtained from microtremor array observation. History After the pioneering work by Kannai and Tanaka,Tokimatsu, K., 1997. Geotechnical Site Characterization Using Surface Wave. Proc., 1s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ambient Vibrations
In geophysics, geology, civil engineering, and related disciplines, seismic noise is a generic name for a relatively persistent vibration of the ground, due to a multitude of causes, that is often a non-interpretable or unwanted component of signals recorded by seismometers. Physically, seismic noise arises primarily due to surface or near surface sources and thus consists mostly of elastic surface waves. Low frequency waves (below 1 Hz) are commonly called microseisms and high frequency waves (above 1 Hz) are called microtremors. Primary sources of seismic waves include human activities (such as transportation or industrial activities), winds and other atmospheric phenomena, rivers, and ocean waves. Seismic noise is relevant to any discipline that depends on seismology, including geology, oil exploration, hydrology, and earthquake engineering, and structural health monitoring. It is often called the ambient wavefield or ambient vibrations in those disciplines (however, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refraction Microtremor
Refraction microtremor (ReMi) is a surface-performed geophysical survey developed by Dr. John Louie (and others) based on previously existing principles of evaluating surface waves and in particular Rayleigh waves. The refraction microtremor technology was developed at the University of Nevada and is owned by the State of Nevada. Optim of Reno, Nevada has the exclusive license to develop the technology, and SeisOpt® ReMi™ has been available commercially from Optim since 2004. Since Rayleigh waves are dispersive, the propagating waves are measured along a linear seismic array and evaluated relative to wave frequency and slowness (or the inverse of the velocity). Due to the dispersive characteristics of higher frequency waves travelling through the more shallow conditions and lower frequency waves passing through deeper materials, a 1-D subsurface profile can be generated based on the velocity with depth. Equipment and Field Procedures The method utilizes equipment typically employ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seismic Microzonation
Seismic microzonation is defined as the process of subdividing a potential seismic or earthquake prone area into zones with respect to some geological and geophysical characteristics of the sites such as ground shaking, liquefaction susceptibility, landslide and rock fall hazard, earthquake-related flooding, so that seismic hazards at different locations within the area can correctly be identified. Microzonation provides the basis for site-specific risk analysis, which can assist in the mitigation of earthquake damage. In most general terms, seismic microzonation is the process of estimating the response of soil layers under earthquake excitations and thus the variation of earthquake characteristics on the ground surface. Regional geology can have a large effect on the characteristics of ground motion.Seed, H. B. and Schnabel, P. B., 1972. Soil and Geological Effects on Site Response During Earthquakes. Proc. of First International Conf. on Microzonation for Safer Construction – ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Sciences
Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres, namely biosphere, hydrosphere, atmosphere, and geosphere. Earth science can be considered to be a branch of planetary science, but with a much older history. Earth science encompasses four main branches of study, the lithosphere, the hydrosphere, the atmosphere, and the biosphere, each of which is further broken down into more specialized fields. There are both reductionist and holistic approaches to Earth sciences. It is also the study of Earth and its neighbors in space. Some Earth scientists use their knowledge of the planet to locate and develop energy and mineral resources. Others study the impact of human activity on Earth's environment, and design methods to protect the planet. Some use their knowledge about Earth processes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
