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- Chen, Pei-shan 50 (%)
- Chen, Pei-Shan 47 (%)
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## Meshing scheme in the computation of spontaneous fault rupture process

### Acta Seismologica Sinica (2008-09-01) 21: 449-455 , September 01, 2008

The choice of spatial grid size has been being a crucial issue in all kinds of numerical algorithms. By using BIEM (Boundary Integral Equation Method) to calculate the rupture process of a planar fault embedded in an isotropic and homogeneous full space with simple discretization scheme, this paper focuses on what grid size should be applied to control the error as well as maintaining the computing efficiency for different parameter combinations of (*D*_{c}, *T*_{e}), where *D*_{c} is the critical slip-weakening distance and *T*_{e} is the initial stress on the fault plane. We have preliminarily found the way of properly choosing the spatial grid size, which is of great significance in the computation of seismic source rupture process with BIEM.

## Variation of shearwave splitting in earthquake clusters with very similar waveforms

### Acta Seismologica Sinica (2000-09-01) 13: 536-543 , September 01, 2000

Among the records of aftershock observation of the 1991 Datong, China *M*_{L}=5.8 earthquake, very similar waveforms from clusters of small earthquakes were found. Cross-correlation of the waveforms of each pair in the cluster confirmed the similarities. Re-sample technology is used to improve the sampling rate, which is helpful to distinguish the small variation of shear wave splitting. The variation of shear wave splitting could be found directly from seismograms of each pair in a cluster.

## Research on nonlinearR/S method and its application in earthquake prediction

### Acta Seismologica Sinica (1995-11-01) 8: 653-658 , November 01, 1995

### 4 Conclusions

The preliminary result of this work was obtained in 1992. At Consulting Meeting for Seismic Trends of China in Jan. 1993, we handed in a report and predicted that “Until now, the average magnitude curve
$$\bar M$$
haven’t gotten risen again after a fall, and the value of*H* is under 0.4, so no alarm is made by each of these two. We predicted that, seismicity of the Chinese mainland in 1993 may be at the same level as in 1991–1992, or a little higher than it, but mustn’t be very high; this is to say that no earthquake with*M*_{s}⩾7.2 will occur in the Chinese mainland in 1993.”

The real situation is: No earthquake with*M*_{s}⩾7.2 occurred in the Chinese mainland, and it shows that this real prediction is true.

To state succinctly: (1)In ths paper nonlinear*R/S* fractal method is applicated in earthquake prediction, and two algorithms RSH and RSHM are proposed. (2)*R* values of this two algorithms reached a notable value, and pass confidence test, so a certain efficiency is presented. But RSHM is some better. (3) It is presented by the successful prediction example that there is a good prospect in predicting with fractal method.

## Seismicity and focal mechanism in Tibetan Plateau and its implications to lithospheric flow

### Acta Seismologica Sinica (1993-05-01) 6: 261-287 , May 01, 1993

The Tibetan Plateau is characterized by its high seismicity produced by the continental collision still working at Himalaya. As seismology had made great contribution to the global tectonics in 1960s, it may also provide some improtant clues to the evolution and tectonics in continents. The present paper summarizes the seismicities, focal mechanisms and neotectionics in Tibetan Plateau. The authors suggest a new classification of the seismic belts or zones in the Plateau.

The belt from Yadong to Anduo is an active seismic belt. The features of neotectonics and focal mechanisms are different on the west of this belt to the east of it. Most of the earthquakes with focal depth*h*>70 km in the Plateau situate on this belt. Different to Yuma, Arakan, the earthquakes with*h*>70 km in Yadong-Anduo belt are less and smaller, their focal mechanisms are normal faults. Appearance of earthquakes with h>70 km suggests that the uppermost mantle in this belt is unstable and the material is hard enough to accumulate strong strain energy.

The authors stress the significance of the northwest-southeast striking fault zone of Yanshiping-Changdu. Several large earthquakes occurred in this fault zone are characterized by left-lateral strike slips. It is the southest one of the several left-lateral strike slip zones in the eastern Tibetan Plateau, and may represent the latest produced one of the left-lateral strike slip zones.

South to the Bangong-Nujiang suture, the fault zone of Bengcuo-Jiali is a belt of discontinuous right-lateral strike slips with very strong seismicities. The pair-faults of Yanshiping-Changdu left-lateral strike slips and Bengcuo-Jiali right-lateral strike slips provide an evidence of the eastward flow of materials in the lithosphere of Qiang Tang terrain between the pair-faults.

Altyn Tagh, Kun Lun and Xianshuihe may represent the residuals of the boundaries of ancient flow paths. Since the sutures and also the cooling effects were produced progressively from the north to south, the flow paths will move progressively southward during the geological times.

## An introduction to the Sino-US joint project “Lithospheric structure and dynamics in Tibetan Plateau”

### Acta Seismologica Sinica (1993-05-01) 6: 249-250 , May 01, 1993

## Geometric effects resulting from the asymmetry of dipping fault: Hanging wall/ footwall effects

### Acta Seismologica Sinica (2008-05-01) 21: 275-282 , May 01, 2008

Root-mean-square distance *D*_{rms} with characteristic of weighted-average is introduced in this article firstly. *D*_{rms} can be used to capture the general proximity of a site to a dipping fault plane comparing with the rupture distance *D*_{rup} and the seismogenic distance *D*_{seis}. Then, using *D*_{rup}, *D*_{seis} and *D*_{rms}, the hanging wall/footwall effects on the peak ground acceleration (PGA) during the 1999 Chi-Chi earthquake are evaluated by regression analysis. The logarithm residual shows that the PGA on hanging wall is much greater than that on footwall at the same *D*_{rup} or *D*_{seis} when the *D*_{rup} or *D*_{seis} is used as site-to-source distance measure. In contrast, there is no significant difference between the PGA on hanging wall and that on footwall at the same *D*_{rms} when *D*_{rms} is used. This result confirms that the hanging wall/footwall effect is mainly a geometric effect caused by the asymmetry of dipping fault. Therefore, the hanging wall/footwall effect on the near-fault ground motions can be ignored in the future attenuation analysis if the root-mean-square distance *D*_{rms} is used as the site-to-source distance measure.

## Grid dispersion in generating finite-differences synthetic seismograms

### Acta Seismologica Sinica (1994-08-01) 7: 397-407 , August 01, 1994

In order to obtain a finite-difference synthetic seismogram, the finite earth model must be subdivided into cells. If the cell size becomes too large in comparison with wavelength of the source signal, waves disperse with increasing traveltime. This phenomenon is known as grid dispersion. The grid dispersion produces a variation of velocity with different frequencies; that is the higher signal frequencies travel more slowly than the lower signal frequencies. Consequently, substantial tailing of the signal arises with increasing traveltime. This may happen if: (1) the grid spacing is large; (2) the sampling rate is large; or (3) the source wavelength is too short compared with grid size. In other words, an important parameter in generating finite-difference synthetic seismograms is the number of grid points per wavelength of the source signal. In this paper, it is shown that the frequency of a source function has great effects on grid dispersion when P-Sv coupled waves propagate through elastic models by finite-differences. The two-dimensional elastic models considered in this paper consist of: (1) a normal fault, and (2) a layer over a half-space. This study verifies that, when generating finite-difference synthetic seismograms, the grid dispersion will be reduced to a satisfactory level if the grid points per wavelength at the half-power frequency of the source signal for the lowest velocity of the medium exceeds ten.

## Evaluation of micro-behavior of strain field in Chinese mainland with the GPS time series

### Acta Seismologica Sinica (2006-09-01) 19: 514-521 , September 01, 2006

Based on the time series of GPS station coordinate in the intemational Earth reference frame (ITRF), we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show that the annual micro-behavior of strain field is divided into two parts by the north-south earthquake belt in the research region. The prevailing direction of compressive principal strain field is nearly consistent in the western region. From west to east, the direction varies from NS to NE. It is in accordance with the direction of the modern compressive principal strain field. This suggests that geologic deformation in western region was mainly caused by that India tectonic plate pushes the research region northward and the Siberia plate pushes it southward relatively. It is an inheritance of new tectonic motion. The prevailing direction of the compressive principal strain field does not exist in the eastern region. The annual biggest shear strain is different greatly in every grid-cell. The values varies from 4.13×10^{−8} to 7.0×10^{−10}. By and large the annual biggest shear strain in the western region is bigger than that in the eastern region. And so is the variation between any two consecutive biggest annual shear strains in the same grid-cell. The annual surface dilatation show that in most grid-cells of the research region the surface dilatation is in compressibility, and the variation between any two consecutive annual surface dilatation in the same grid-cell is small.

## Study on the characteristics of rock failure strain and acoustic emission field for two parallelling faults with the same slip direction including asperities

### Acta Seismologica Sinica (2002-07-01) 15: 374-382 , July 01, 2002

By dealing with strain and acoustic emission (AE) data for two parallelling faults’s instability and failure with the same slip direction including asperities, the temporal-spatial evolution of strain and AE field distribution on the asperity of parallelling faults is analyzed. Furthermore the failure process of asperities and interaction among the asperities, *i.e.*, positive and negative seismicity are discussed. Results show that instability and failure for the parallelling faults is a kind of negative seismicity.

## An inversion of site response and Lg attenuation using Lg waveform

### Acta Seismologica Sinica (2007-11-01) 20: 605-616 , November 01, 2007

Based on spectral ratio method, a joint inversion method was used to obtain parameters of Lg wave attenuation and site response. The inversion method allows simple and direct (two-parameter) determination of Lg wave attenuation and site response from sparse spectral data, which are not affected by radiation pattern factor and different response of same instrument after geometrical spreading. The method was used successfully for estimating site response of stations of Zhejiang Seismic Network and measuring Lg wave attenuation. The study is based on 20 earthquakes occurred in northeast of Taiwan with magnitude *M*_{S}5.0–6.7 and 960 seismic wave records from 16 stations in Zhejiang area from 2002 to 2005. The parameters of site response and Lg attenuation were calculated with a frequency interval of 0.2 Hz in the range of 0.5 Hz to 10 Hz. Lg wave attenuation coefficient corresponding to U-D, E-W and N-S components are *γ*(*f*)=0.00175*f*^{0.43485}, *γ*(*f*)=0.00145*f*^{0.48467} and *γ*(*f*)=0.0021*f*^{0.41241}, respectively. It is found that the site response is component-independent. It is also found that the site response of QIY station is significant above the frequency of 1.5 Hz, and that the site response of NIB station is low for most frequency