Study On Decomposition Of Groundwater Level And Pre-earthquake Anomaly

Earthquake is the process of crustal movement of rock stress-strain continue to accumulate, enhancement, when it exceeds the maximum strength of rock can bear, the Earth's interior dramatic breakdown of local media to generate seismic waves, which in a certain range of phenomena caused by ground vibration. A large number of observations and studies have shown that sensitive records of both underground fluids, but also modulation and trigger crustal stress-strain changes, although not yet fully understand the various earthquake related groundwater level abnormal formation mechanism, but with the potential of earthquake prediction the socio-economic value, as in-depth study and understanding of the continuous improvement of the level of use of the abnormal changes in groundwater level to carry out earthquake precursors prediction is very meaningful.In this paper, an analysis of influencing factors on the water table, using wells-aquifer system of rock mechanics-the hydrodynamic coupling theory analysis of major non-tectonic effects of stress on the well water level in the mechanism of water wells were deduced with the tidal force and pressure changes in analytical solution. Then according to non-tectonic stress features such as high-frequency and periodicity, it is estimated well water level for various major non-tectonic stress response factor, and thus from the well water level data to tidal force, pressure and rainfall impact it will break down out to be simply a matter of the well water level caused by tectonic stress change data. On this basis, that have been the elimination of non-tectonic stress (mainly atmospheric pressure, tides, rainfall) caused by changes in the well water level data, combined with earthquake zone hydro-geological, engineering geological characteristics, from the abnormal changes of tectonic stress before theearthquake point of view, analysis of tectonic stress under the action of water level changes; the same time, the use of response factors contained in the physical quantity of rock mechanics and dynamics of changes in water-well water level changes, analyze the causes of pre-earthquake water level anomaly to explore the pre-earthquake water level anomaly identification method, for the use of the groundwater table dynamics provide the basis for earthquake prediction based on.Obtain the following conclusions:(1) Respectively analytic solution to Well-water level Changes under Earth Tide Stress and Barometric Pressure.An analytic solution to Well-water level Changes under Earth Tide Stress:△h=[E+(E-E)e-A(?)](△ψ2/g).An analytic solution to Well-water level Changes under Barometric Pressure:△h=-(1-β)(1-e-4T△t/rw2)△p.(2) Decomposition of water tableBy Yimen, Nanxi and Deyang, three observation wells in the data analysis, respectively using a regression analysis method and wavelet analysis on the Yimen, the use of binary regression analysis methods and wavelet analysis on the Nanxi, the use of the state of spatial analysis methods and wavelet analysis on the Deyang, the aim is separation the non-structural factors impact on the well water level, aimed at testing and comparing the effects of these three methods of decomposition. Contrast to the above-mentioned three observation wells and decomposition of the original water level curve after the water level curve, the water level of decomposition is not only more smooth curves and volatility of smaller, more used to describe the changes in tectonic stress. In the domestic application of regression analysis and wavelet analysis of data dealing with seismic observation wells are very common, but very few state-space analysis applications, so this state-space analysis of a detailed description.(3) Groundwater level precursory anomalies identified At 14:28 on May 12,2008, a major earthquake-Ms8.0 occurred in Wenchuan County, Sichuan Province. In this paper, by the date analysis of the observation wells,such as, Qionglai, Luguhu, Nanxi, Deyang, and Xichang, taking into account Qionglai Well water level of the pressure to respond to well, it is calculated using pressure coefficients to carry out unusual recognition; taking into account the lake water level of the gravity well of earth tide response to well water level changes in response to the tide changes, it is unusual method of using tidal distortion to carry out an exception identification; take into account the well water level Nanxi response to the tidal force and pressure very well, so use of binary regression analysis and wavelet analysis, well water level data from the original break out the impact of tidal force and pressure to carry out an exception recognition; right Deyang well with state-space analysis and wavelet analysis separated tidal force, pressure and rainfall influence to abnormal recognition; pairs well with water level in Xichang tidal loading and unloading response ratio, for an exception identification. Based on the above-mentioned five observation wells in identifying the abnormal findings were:(1) The well water table of the Qionglai occurred short-term anomaly before the earthquake; (2) The well water table of the Luguhu occurred short-term anomaly before the earthquake; (3) The well water table of the Nanxi has not anomaly before the earthquake; (4) The well water table of the Deyang has obvious short-impending anomaliy before the earthquake; (5) The well water table of the Xichang occurred short-term anomaly before the earthquake;...