Study Of Near-Fault Strong Earthquake Ground Motion

Near-fault ground motion has been very active in the field of seismology and earthquake engineering research for the past ten years. At the end of the last century and the beginning of this century, we witnessed many destructive earthquakes and had gained many valuable strong motion records for a solid basis of the near-fault strong ground motion. This paper, based on Wenchuan earthquake data in 2008, combined with some other domestic and foreign earthquake data, made near-fault earthquake detailed analysis, such as velocity pulse, attenuation relations, basin effects, etc. Primary Work is summarized in this article now:1. By direct statistical analysis of near-fault pulse-type earthquakes recorded, combined with my proposal of "proportion of the number of" concept, this paper obtained the affected area of the pulse-type records and relationship of the pulse parameters and the fault distance. It is obvious regularity that acceleration records numbers with velocity pulses (proportional number) increases with the reduction of the fault distance. When the fault is greater than 40 km away, the frequency of the appearing pulse records is very small. Beyond this range, the velocity pulse seems to be negligible. it is very obvious that pulse peak with the increase of the fault distance decrease. Whether Chi-Chi earthquake or Northridge earthquake, the peak attenuation (PGV and Vp) are generally faster, particularly in the NS direction. Therefore, at the view of pulse peak, the impact is constantly decreasing with distance.2. This paper presents a simple simulation method of pulse-type time, and verifies the feasibility of through a simple random component added to the pulse components to simulate the original seismic data. Simple simulation of this chapter, the differential method, the displacement angle inverses the acceleration. Simulated data and original data, whether numerical or the response spectrum, are relatively close. Since the concept of differential produce in the settlement of the conflict in the direct and curve, small local lines can be used to approximate the curve, it is the direct application of linear functions. It can be feasible verified by simple random component added to the pulse components to simulate the original seismic data. 3. This paper puts forward improved Makris and Roussos pulse simulation model (Mirror Image Method). This way don't introduce new function and increase the complexity of the model, making Makris and Roussos model in simulating the near-field earthquake greater flexibility, better used to simulate near-fault earthquake records. In addition to Mirror Image Method, the paper also explores the model of Makris and Roussos based on the composition and evolution, to make the original model better adaptability.4. This paper analyzes in detail the characteristics of ground motion records of the main Wenchuan earthquake in Sichuan Province, but also compared other major earthquake at home and abroad. In particular, the introduction of the concept of multi-peak point average makes the analysis of attenuation and gives relationship of points and the peak attenuation. Finally, this paper uses the five-point average peak to explain why the possibility of serious damage in Wenchuan earthquake.5. This paper explores a new ground motion attenuation relation of the statistical approach, using a weight floating consideration. Ground motion located local site, is the relationship with the epicentral distance and fault distance, but the difference of their contribution. First, this paper defines a new distance, the use of floating weight coefficient from the epicenter and the fault together; get this one variable -- "Weight Distance". With the "Weight Distance" instead of the epicenter or fault distance, we analysis ground motion attenuation relation ,verifying using standard deviation and the correlation coefficient, and using these two indicators to determine the optimal weight coefficient and getting the best weight distance. Attenuation method using this floating is out of the original unity of the shackles of the statistical regression, using the best weight distance to get the best attenuation relationship.6. By a simple "lift coefficient", this paper proposes amendments to the specification spectrum, mainly for the impact of the fault distance. However, as the provisions of the United States UBC97 need to consider the near field the Zone4, mainly distributed in the territory of the West Coast like California, we discuss the program area also considering near the main fault zone range. This adjustment was targeted.7. This paper explores the basin effect of near-fault earthquake. According to earthquake disaster first-hand information on field trips, by the different geographic location, we divided the cities into three categories: basin inside (Chengdu), the basin margin (Dujiangyan, Mianzhu, Jiangyou, Shifang), the external basin (Beichuan). Damage from a macro perspective of the basin is considered, especially apparent edge effect; damage is more serious, relatively light in the inside of the basin. In the mountains, damage is more serious than in the plain, especially the two relatively close distances between the mountain areas. In addition to earthquake disasters, landslides,mudslides and other secondary disasters are also very serious.