Review and Proposed Method to Study the Damage Orientation of Earthquake Effects in Pre-Instrumental Earthquakes.

The information and seismic parameters gained from pre-instrumental earthquakes are essential to improve the seismic catalogs and hazard studies. The earthquake damage (ED) that affected architectonic elements during earthquakes (e.g. fallen walls, conjugated fractures in walls, dropped keystones in arches), and when this earthquake damage is orientated (EDO), can be used to infer seismic parameters of pre-instrumental earthquakes such as epicenter location, seismogenic source or ground motion. However, there is not a common methodology to measure this orientation damage. For example, tilting and fallen walls are some of the most used elements to infer the horizontal ground motion in non-instrumental earthquakes. Nevertheless, according to the shape of the architectonic element (a wall in this case), it has only two degrees of freedom to fall, and therefore, its azimuth does not necessarily fit with the ground motion pulse orientation. In this work, a review of the earthquake damage (ED) and effects described in pre-instrumental earthquakes is carried out. A method is also proposed, considering not only the frequency of damage orientations but also considering the uncertainty angle of each element to be damage. The ED has been classified into five groups according to the angle of uncertainty to record the pulse orientation. This method has been checked taking advantage of recent earthquakes with a good instrumental record of the ground motion pulse, and also tested modeling different scenarios with different pulse orientations. This method, that takes into account the uncertainty angles, is a reliable method to calculate the EDO and back-calculate the ground motion pulse orientation in pre-instrumental earthquakes in absence of more accurate modern instrumental records. This method can also be useful for seismic risk assessment and restoration and protection of historical heritage. [ABSTRACT FROM AUTHOR]