2012 Vol. 34, No. 1

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Rydelek-Sacks test for the periodicity distinguishing of northeastern China earthquakes and study on their magnitude-time periodical spectrum
Li Yutongup,  Jiang Changshengupdiv
2012, 34(1): 20-30.
For distinguishing the potential periodicity and the relationship between shallow and deep earthquakes in northeastern China, this paper conducted the Rydelek-Sacks test based on various earthquake catalogues to consider the influence of selected magnitudes on the periodicity. The test for the periodicity distinguishing was investigated by using shallow earthquakes from 1970 to 2009 with magnitude no less than ML4.5, 1920 to 2009 with magnitude no less than MS5.0 and deep earthquakes from 1905 to 2009 with magnitude no less than MS6.0. Major results of our study are: ① Deep earthquakes in northeastern China region have an obvious and stationary active period; ② Periodicity of shallow earthquakes probably depends on magnitude; ③ Good correlation between deep earthquakes and ML4.5mdash;5.0 shallow ones show that in northeastern China deep earthquakes may influence on the shallow earthquakes with magnitude even lower than MS5.0. This fact is beyond our traditional knowledge.
Stability of sparse station data inversion for deviatoric moment tensor solution of regional earthquakes
Zheng Jianchangup,  Chen Yun-taiayloansc
2012, 34(1): 31-43.
Observations from regional seismic network are used in studying deviatoric moment tensor for the MW5.4 earthquake of 26 Febuary2010 inTaiwanadjacent area. The smallest rotation angle defined by Kagan (1991) between our result and the Havard GCMT solution is 9.5deg;, and the focal depth we determined is41 km, which is close to USGS location result and possibly closer to the real source. The paper also discusses the effect of station distribution on deviatoric moment tensor inversion by selecting different station combinations. The result shows that, for the data sets from three 3-component stations, the solutions are mostly accurate. The better station coverage, the less departure from real solutions. In appropriate case, the data set from two 3-components stations may result in relatively reliable solution.
A study on vertical-component P-wave receiver functionof small-aperture seismic array and its application
Qin Manzhong Zhang Yuanshengup,  Shen Xuzhangup,  Wei Congxinup
2012, 34(1): 44-51.
The vertical-component P-wave receiver function technique is used to extract the Moho multiples (PpPmp phase) and determine thickness of the crust beneath the Lanzhou Seismic Array. The multiples (PpPmp phase) are determined with waveforms from 16 teleseismic deep earthquakes, and then the average crust thickness is estimated, which value is about (51.6plusmn;1.8) km. This result is also consistent with the result of previous studies.
Statistic distribution of non-empty grid numbers for earthquakes and quantitative test on enhanced and quiescent acivity
Jiang Haikun Wu Qiong Song Jin Qu Junhaoup Li Jinupdivp
2012, 34(1): 52-63.
Based on the earthquake data during 1980mdash;2010 in North China region, we use the grids with ltimes;l unit size to cover the area and investigate the variation of non-empty box number of earthquakes. When grid size l is small enough, the number of non-empty boxes tends to be equal to earthquake frequency. When grid size l is large enough, the number of non-empty boxes will be close to 1. This study shows that the influence of grid size on result stability is very weak when l isge;0.5deg;. The variation of non-empty boxes is related to the expanded (enhanced) or constricted (quiescence) patterns of earthquake spatial distribution. The numbers of non-empty boxes with different l roughly show a consistent changing tendency, potentially reflect the stress perturbation or undulation during a short time period indirectly. Small earthquakes are much more clustered, the difference between results with different threshold magnitude gradually tend to be small when threshold magnitude increases gradually. The non-empty grid numbers show a normal distribution, therefore the normal distribution range for non-empty grid numbers can be calculated with the given confident probability and the abnormal could be detected if the data is outside this normal range. The statistics show that in North China the forecasting efficiency is low for quiescence type abnormal, the enhanced type abnormal has a higher correct alarm rate, and the precursory criterion both by enhanced and quiescence type abnormal has a higher forecasting efficiency. This means that the precursory of small or moderate earthquakes before large earthquakes mainly displays as enhanced activity. The results also show that the pattern change of small or moderate earthquake spatial distribution seems to be related to coming large earthquakes more tightly.
Study of ground surface tilts from strong motionrecords of the Wenchuan earthquake
Peng Xiaoboup,  Li Xiaojunup2, commult
2012, 34(1): 64-75.
Based on the difference of dynamic response to tilts between horizontal pendulums and vertical pendulum, spectral ratio method was applied to estimate the coseismic surface tilts deduced from strong motion records of the Wenchuan earthquake. The result shows that the ground surface tilts are generally less than 1 degree and mainly appears within30 kmto fault rupture surface traces, while rarely discovered in the area outside100 kmor root-mean-squared horizontal peak accelerations are less than200 cm/s2. The frequency band influenced by tilts is less than 0.1 Hz. In general, tilts in hanging wall is greater than that in footwall in near fault areas, and tilts in normal direction of fault is less than those in parallel direction. The spectral ratio of Qingping station located between central fault and front mount fault is relatively low and stable, which may imply ae special movement feature of the area. The tilts of Wolong station may be controlled by deformation transition from the hanging wall to laterally stationary area. Comparison of tilts between the stations at reverse and strike slip fault segments showed that the tilts may be influenced by local site condition.
Application of multiple ground motion factors in earthquake-induced landslide hazard evaluation/t
Wang Xiuying Nie Gaozhongup Ma Mujunup
2012, 34(1): 76-84.
Earthquake-induced landslide is a catastrophic earthquake secondary disaster. The triggering factor of earthquake plays very important role in this kind of disaster. Many parameters can represent the influence factor of the earthquake. However, there are differences among their representative capabilities, which will exert great influence on the evaluation/forcasting result if these parameters are used. A method of combining the parameters into one is given based on Analytic Hierarchy Process (AHP). The discrepancy and difference between parameters can be compensated in this way. The calculated example shows that the result based on the combination of these parameters is far better than those obtained from single ones. This proves the feasibility of applying this method to evaluation of other kind of earthquake hazards.
A study on method of signal denoising based on wavelet transform for micro-seismicity monitoring in large-scale rockmass structures
Xu Hongbin Li Shulin Chen Jijingup
2012, 34(1): 85-96.
This paper applied wavelet denoising method to monitoring micro-seismicity in large-scale rockmass structure. The feasibility of using symlet6 inwavelet denoising was validated with MATLAB simulation. Then four types of adaptive threshold rules for wavelet denoising are used to denoise three noisy signals. The result shows that the noise in signals can be filtered effectively with the four threshold rules and the Rigrsure threshold for wavelet denoising is more effective with the least mean square deviation and highest signal to noise ratio. Based on the multi-channel digital microseism monitoring system in Shizhuyuan mine, this paper applied wavelet denoising method to three different microseismic signals with the result of MATLAB simulation. The results show that the true microseismic signals can be recovered from the noisy signals by removing noise at every wavelet scale, even though noisy signals have low signal to noise ratio or include wide frequency range. The wavelet threshold denoising is suited especially to the denoising of microseismic monitoring signals in large-scale rockmass structures.
Significance of 3D seismic exploration in urban active fault fine locating
Liu Ying Shen Yuexiaup Niu Xiaojunup
2012, 34(1): 97-104.
Present state of urban active fault survey is reviewed. Some problems of unban active fault fine locating by using 2D seismic exploration are presented, such as poor controlling of small-scale structures in middle-shallow strata, insufficient precision of fault homing in steeply dipping strata, inaccurate fault location coming from oblique intersection between surveying lines and fault strike due to existing buildings and other obstacles, and inadequate constrain on fault breakpoint, intersection position and endpoint due to sparse surveying grids. Advantage of 3D seismic exploration is analyzed theoretically. The problem of inaccurate fault location, induced by limitation of 2D seismic exploration, surface environment and geological conditions, can be solved by using 3D exploration. The feasibility and significance of using 3D seismic exploration in urban region is demonstrated through example analysis in data acquisition, instrument selection, geometry design, optimizing design, field quality monitoring, special data processing and good geological effects.
Discussion on the problem of frequent earthquakes in seismic design
Shi Shuzhong Shen Jianwenupcom mult
2012, 34(1): 105-110.
Small earthquakes used as the standard of section seismic checking in seismic design confuses two significantly different concepts. One is the ground motion parameters corresponding to 63% exceeding probability in 50 years (hereinafter referred to as frequent earthquakes), and the other is the parameters received by reducing that corresponding to 10% exceeding probability in 50 years (hereinafter referred to as reduction small earthquakes). Above confusion leads to a result that two different standards are actually followed in seismic design. Complexity of the relation of ground motion parameters corresponding to medium and small earthquakes is discussed, such as dispersion of peak acceleration, differences of consistent probability spectra on the bedrock obtained from seismic hazard analysis, and systematic differences of site-related response spectra between medium and small earthquakes by soil non-linear effect. Substitution frequent earthquakes for reduction small earthquakes in section seismic checking for major engineering projects may result in underestimation of response spectrum characteristic period Tg. Some suggestions are put forward.
Discussion on focal mechanism solutions and seismogenic structure of 24 Jan 2010 Hejinmdash;Wanrong, Shanxi, MS4.8 earthquake
Song Meiqin Zheng Yongup Li Bin Su Yan  Wang Xiaoshanup Luuml; Fang Zhao Xiaoyun
2012, 34(1): 111-117.
Compilation of Chinese historical earthquake data by building up a database system based on seismic intensity points
Lin Guoliang Wang Jian hr
2012, 34(1): 118-124.
Strong earthquake activity all over the world and strong-moderate earthquake activity within and near China (Septembermdash;October,2011)
2012, 34(1): 125-126.
Comparison on characteristics of strong ground motion from two earthquakes with similar MW: the Baja, Mexico, MW7.2 and Yushu, China, MW6.9 earthquake in 2010
Meng Lingyuan Shi Baoping
2012, 34(1): 1-19.
The 4 April 2010 MW7.2 Baja, Mexico, earthquake occurred in northern Baja California at shallow depth along the principal plate boundary between North American and Pacific plates, and two people were killed in the Mexicalia area. The 14 April 2010 MW6.9 Yushu, China, earthquake occurred as a result of strike-slip faulting in tectonically complex region of the eastern Qingzang plateau. At least 2 220 people were killed in Yushu area till April 25, 2010. International media reports of such kind of disasters by Yushu earthquake is resulted from poor building structure design comparing with Mexicalia area. In fact, although the moment magnitude of Yushu event is similar to the Baja event, the radiated seismic energy from Yushu fault dynamic rupture is almost 10 times of the Baja earthquake, resulting stronger near-fault ground motions. In this paper, two special finite fault models with the same size in fault length and width are constructed to simulate the near-fault strong ground motions for comparison study. The fault slip distributions on both faults are generated based on a dynamical composite source model, in which the subevent-source-function is described by Brunersquo;s pulse. Our result shows that the near-field peak ground accelerations (PGAs) and peak ground velocities (PGVs) on bed rocks from Yushu event are almost twice as that from Baja event. Moreover, if the shallow velocity structures (V30, average shear-velocity down to 30 m) are considered in the strong motion simulation, the resultant PGAs and PGVs from Yushu event are also twice as that from Baja event. Therefore, the radiated seismic energy plays a significant role in determining the levels of strong ground motions, in which stronger ground accelerations usually cause much more property damages on the ground. The source rupture dynamics related to the frictional overshoot and undershoot is discussed and used to constrain source parameters such as the static stress drop and dynamic stress drop. It needs to point out that, in addition to the moment conservation applied on the main fault, the measurement of radiated seismic energy or apparent stress should be added to the numerical simulation in order to obtain physically realistic result. The numerical modeling developed in this study has a potential application in ground motion estimation/prediction for earthquake engineering purpose.