The influence of the kłodnica fault tectonic zone on the degree of damage to buildings resulting from high magnitude tremors Wpływ strefy tektonicznej uskokukłodnickiego na wielkość uszkodzeń w budynkach spowodowanych wysokoenergetycznym wstrząsem Abstract On 18 April 2015, a regional tremor with an energy E=4·10 9 J occurred in the main saddle of fault VIa. This phenomenon emerged as result of summing up of stresses caused by underground exploitation conducted in the vicinity of natural faults with unrelaxed tectonic stresses, which resulted in the very strong influence of this tremor on the surface infrastructure and on the emotional well-being of local people. This analysis suggests that there is a statistical relationship between these values. Diversity of location both of the size of measured vibration parameters, damages in the buildings and of feelings of the vibrations prove an unequal radiation of the seismic waves caused by the amplifying influence of the fault zone. Keywords: mining tremors, tectonic faults, mining damageStreszczenie 18 kwietnia 2015 r. w strefie uskokowej uskoku VIa w siodle głównym wystąpił wstrząs regionalny o energii E=4·10 9 J. Zjawisko to miało miejsce w wyniku sumowania się naprężeń wywołanych podziemną eksploatacją prowadzoną w otoczeniu naturalnych uskoków z niezrelaksowanymi naprężeniami tektonicznymi, co miało przełożenie na bardzo silne oddziaływanie tego wstrząsu na infrastrukturę powierzchniową i odczucia przez ludzi. Przeprowadzona analiza wykazała, że istnieje statystyczny związek między tymi wielkościami. Zróżnicowanie położenia zarówno wielkości pomierzonych parametrów drgań, uszkodzeń w budynkach, jak i odczuć wstrząsów świadczą o nierównomiernej radiacji fal sejsmicznych spowodowanej amplifikującym oddziaływaniem strefy uskokowej.Słowa kluczowe: wstrząsy górnicze, uskoki tektoniczne, szkody górnicze 54

Seismic energy propagation from the hypocentre of mining-induced tremors usually causes an uneven distribution of the peak ground velocity PGVHmax in tectonically complicated structures, and consequently, an uneven distribution of damage to buildings located on the ground surface. This study aimed to estimate the impact of high-energy mining-induced tremors in fault zones on damage to buildings. In the study, we describe a case of one of the highest-energy mining-induced tremors E = 4.0 · 108 J (local magnitude ML = 3.6) that occurred in the Upper Silesian Coal Basin (USCB), Poland. The hypocentre of the tremor was most probably located in the Barbara fault zone, one of the larger faults in that western part of the USCB. Numerous damaged buildings on the terrain surface were registered, both in the epicentral zone and at a greater distance from the epicentre, mostly from the southern side of the Barbara fault zone. We calculated that the tremor was characterised by a normal slip mechanism associated with the same kind of fault as the Barbara fault. The azimuth of the nodal planes was similar to the west-east direction, which is consistent with the azimuth of the Barbara fault. From the focal mechanism, the greatest propagation of seismic energy occurred in south and west-east directions from the tremor hypocentre towards the surface. It was found that from the northern side of the hanging wall of the Barbara fault, there were 14 instances of damage (19%), and in the southern part of a hanging wall, there were 58 (81%). Therefore, the directionality of seismic energy propagation is aligned with the focal mechanism acting in the Barbara fault. It has also been concluded that a width of the zone of up to about 1200 m along the Barbara fault is the most threatening on the basis of registered building damage in the geological conditions of USCB. The study has shown that in assessing the impact of mining-induced tremors on buildings and the environment, the disturbance of seismic energy propagation by larger faults should be considered.