Building damage patterns depending on faulting types and seismic waves induced from medium scale earthquake damages

Earthquakes produce a variety of hazards to human society around the epicenter even though the magnitude of the earthquake is in a range of medium scale (M=5 6). Especially, in developed countries the amount of building damages including infrastructures is greatly increasing due to highly costing structures and tall building. Furthermore, the importance of the damages of historical heritages and nuclear facilities are countless. Therefore, many countries invest a lot of money for anti-earthquake designs. Although many literatures reported earthquake induced building damage patterns and their controlling factors in view of construction, there are not so many researches on tectonic or structural controlling factors. Therefore, we carefully analyzed the building damage patterns induced by two medium scale earthquakes in Korea, associated with different faulting types (Gyeongju earthquake, M_L=5.8, 12^th Sept. 2016, strike-slip faulting; Pohang earthquake, M_L=5.4, 15^th Nov. 2017, reverse faulting). From the earthquake damages, we found several very systematic and interesting damage patterns; Riedel type fracturing indicating horizontal shear on wall of many buildings associated with the earthquake of the strike-slip faulting and high angle (conjugate) fracturing indicating vertical compression on building walls associated with the earthquake of the reverse faulting. Furthermore, these building fracturing patterns are wholly different from the crustal or rock fracturing associated with the fault types. Based on our analysis and interpretation of these facture patterns, the damage patterns are strongly dependent on induced surface deformation and seismic waves or ground slip associated with the earthquakes, because the propagation of the induced stress and seismic waves or ground slips are different depending on the related faulting types. The stress conditions within the crust and around buildings are wholly different, passing through the surface, because building exist on the free surface without horizontal stresses. This kind of study can be very helpful for anti-earthquake designs, if we know the dominant tectonic setting or regime of a certain area.