دانلود رایگان مقاله انگلیسی جهت گیری آسیب زلزله برای پی بردن به پارامترهای لرزه ای در مکان های باستانی و زلزله های تاریخی - الزویر 2018

ABSTRACT

Studies to provide information concerning seismic parameters and seismic sources of historical and archeological seismic events are used to better evaluate the seismic hazard of a region. This is of especial interest when no surface rupture is recorded or the seismogenic fault cannot be identified. The orientation pattern of the earthquake damage (ED) (e.g., fallen columns, dropped key stones) that affected architectonic elements of cities after earthquakes has been traditionally used in historical and archaeoseismological studies to infer seismic parameters. However, in the literature depending on the authors, the parameters that can be obtained are contradictory (it has been proposed: the epicenter location, the orientation of the P-waves, the orientation of the compressional strain and the fault kinematics) and authors even question these relations with the earthquake damage. The earthquakes of Lorca in 2011, Christchurch in 2011 and Emilia Romagna in 2012 present an opportunity to measure systematically a large number and wide variety of earthquake damage in historical buildings (the same structures that are used in historical and archaeological studies). The damage pattern orientation has been compared with modern instrumental data, which is not possible in historical and archaeoseismological studies. From measurements and quantification of the orientation patterns in the studied earthquakes, it is observed that there is a systematic pattern of the earthquake damage orientation (EDO) in the proximity of the seismic source (fault trace) (<10km). The EDO in these earthquakes is normal to the fault trend (±15º). This orientation can be generated by a pulse of motion that in the near fault region has a distinguishable acceleration normal to the fault due to the polarization of the S-waves. Therefore, the earthquake damage orientation could be used to estimate the seismogenic fault trend of historical earthquakes studies where no instrumental data are available.

5. Conclusions

Information of the seismogenic source of ancient earthquakes can be obtained by quantifying earthquake damage orientation (EDO) in archaeological sites, historical buildings or historical photographs. This information is of value especially in regions were no fault surface rupture can be identified. This damage can act like structural seismoscopes recording the ground motion pulse, important factor in the design of critical facilities and regulatory seismic codes. However, in the literature, the parameters that can be obtained from the earthquake damages are contradictory depending on the authors and even call into question any relation with the earthquake damage. In the three regions affected by earthquakes studied in this work (Lorca 2011, Christchurch 2011 and Emilia Romagna 2012), the damage caused by the earthquake in historical buildings is systematically oriented in the proximity of the fault (less than 10 km). The EDO is normal (±15º) to the fault trend. The three studied cases show that: (1) The EDO is not oriented toward the epicenters. (2) The EDO is not parallel to the P-waves. (3) The EDO do not present the same orientation as that of the maximum shortening or compressional strain. (4) The EDO is not oriented according to the kinematic of the fault. Therefore, if the EDO is systematically oriented, it can be interpreted as the result of the ground motion, which has an acceleration pulse normal to the fault. This pulse in near fault sites is mainly dominated by the source characteristics with a distinguishable acceleration pulse normal to the fault due to the polarization of the S-waves, therefore can be used to infer the seismic parameters of the source. This way, when the earthquake damage orientation is observed in an archaeological site, it could be used as a quick and preliminary way to estimate the seismogenic fault trend from the other candidate faults with different trends. This information combined with historical and archaeological studies that can determine the timing, intensity and location of the earthquake are of great value in seismic hazard studies where no instrumental data are available and the fault rupture is not recognized.