The Statistical Relationship between the Maximum Amplitude of the Body Strain Record and the Surface-wave Magnitude and Epicenter Distance

Based on the body strain record of Tiantanghe station from 2008 to 2014,we make a statistical analysis of the relationship between the maximum amplitude of the body strain record and the surface-wave magnitude,epicenter distance of the earthquakes,which occurred in the Chinese mainland and its surrounding areas with MS≥6. 0 and the rest of the world with MS≥7. 0. According to statistical results,we propose a statistical formula between the surface-wave magnitude of earthquake and the maximum amplitude of the body strain record,the epicenter distance: M_S~*= 0. 37 ln A_max+ 0. 57 ln D + 0. 07. We can also derive a theoretical estimation formula for the maximum amplitude: A_max=e^(2. 7(M_S^*-0. 07))D^(-1. 54). This demonstrates that the maximum amplitude of the body strain record increases exponentially with the increase of the surface-wave magnitude, and decreases with the increase of the epicenter distance,and shows a negative correlation with their product. We further discuss the necessity of adding instruments with high frequency sampling to earthquake monitoring, and dicuss the prospects for precise earthquake prediction in future.

Analysis of Sacks Body Strain Interference at Beida No.200 Station in Changping and Earthquake Case Study

The relationship between Sacks body strain deformation at Beida No. 200 station in Changping and tidal solids,atmospheric pressure and water level is analyzed in this paper. Sacks body strain deformation data before the M_S8. 0 Wenchuan earthquake is studied based on the analysis of the interference. The short-impending anomaly of the body strain deformation is considered to be reliable. The anomaly characteristics conclude:( 1) The trend anomaly as extensional change of the body strain deformations on a quasi 1 year time scale before the Wenchuan earthquake was recorded, and the accumulative amount was about 4000 × 10^(-9). Correspondingly,the short-term precursor of earthquake was manifested as an extensional abrupt change.( 2) The extensional intermittent anomalous abrupt change was recorded by body strainmeters between March1 and May 7 in 2008.( 3) Four compressional abrupt changes were recorded in the intermittent distortions recorded between April 13 and May 11.( 4) High frequency components were increased in the distortion process in May 1 to 3,5,7,and 9 to 12,caused by slow earthquakes before the Wenchuan earthquake according to wavelet analysis. The abnormal phenomena are summarized and the mechanics discussed in this paper. Strain solid tide distortions in body strain observations,the continuous repeated extensional and compressional abrupt changes accompanying these distortions,and the increase of high frequency components can be regarded as the index of short term and impending earthquake prediction,based on analysis of interference factors such as air pressure and water level.

Study of main body element of crustal strain and its relationship with moderate-strong earthquakes

In this paper, progress in strain study of blocks and faults by GPS data are discussed, and the concept that active structures between blocks are the main body of crustal strain is clarified. By energy transfer principle of elastic mechanics, the relation between strain around faults and tectonic force on fault surfaces is set up and main body element model of crustal strain is constructed. Finally, the relation between mechanical evolution of model and seismogenic process of Kunlun earthquake （Ms=8.1） is discussed by continuous GPS data of datum stations. The result suggests that the relatively relaxed change under background of strong compressing and shearing may help to trigger moderate-strong earthquakes.

A FINITE ELEMENT METHOD FOR STRESS ANALYSIS OR ELASTOPLASTIC BODY WITH POLYGONAL LINE STRAIN——HARDENING

In this paper, the stress-strain curve of material is fitted by polygonal line composed of three lines. According to the theory of proportional loading in elastoplasticity, we simplify the complete stress-strain relations, which are given by the increment theory of elastoplasticity. Thus, the finite element equation with the solution of displacement is derived. The assemblage elastoplastic stiffness matrix can be obtained by adding something to the elastic matrix, hence it will shorten the computing time. The determination of every loading increment follows the von Mises yield criteria. The iterative method is used in computation. It omits the redecomposition of the assemblage stiffness matrix and it will step further to shorten the computing time. Illustrations are given to the high-order element application departure from proportional loading, the computation of unloading fitting to the curve and the problem of load estimation.