NEOTECTONIC ACTIVITY OF THE SKAWA RIVER FAULT ZONE (OUTER CARPATHIANS, POLAND)

作者：Zuchiewicz Witold^*; Tokarski Antoni K; Swierczewska Anna; Cuong Nguyen Quoc

来源：Annales Societatis Geologorum Poloniae, 2009, 79(1): 67-93.

• neotectonics
• morphotectonics
• fractured clasts
• seismic hazard
• Skawa River valley
• Outer Carpathians
• Poland

The Skawa River catchment basin in the Outer West ern Carpathians of Poland is situated upon morphostructures showing differentiated mobility in the Quaternary. Long pro file of river channel reveals the low est values of concavity index among the Polish Outer Carpathian rivers, pointing to low degree of river pro file maturity, particularly in its middle reach coinciding with a zone of abnormally high river bed gradients.
The Skawa River valley utilizes in its middle and north ern reaches the Skawa River Fault Zone (SRFZ) composed of differently oriented oblique-slip faults, visible on DEM images as well-marked, recti linear topolineaments. The NNW-SSE to N-S faults in the Silesian Nappe were probably reactivated in Late Pleistocene times as nor mal faults downthrowing their east ern sides, as shown by ab normally high position of the Weichselian Early Glacial straths on the west ern valley side. Such an episode of neotectonic activity ( late Early Glacial times of the Last Glacial stage) has not been recognized so far in the other river valleys of the Polish segments of the West ern Outer Carpathians. We conclude that some of the NNW-SSE to N-S trending faults were reactivated as strike-slip faults. This would con form to the present day stress arrangement within the Polish segment of Carpathians. Moreover, de formations of the Pleistocene straths be tween Osielec in the south and Wadowice-Zator areas in the north appear to indicate both pre-Weichselian and Weichselian re activation of the Silesian and-to a lesser ex tent - Magura frontal thrusts. These movements continued also in the Holocene, although to a smaller extent, most probably due to moderately strong and/or strong earthquakes of magnitudes exceeding 5.5-5.7, resulting in clast fracturing within Holocene alluvium, particularly strong on the Silesian frontal thrust, and less intensive on the Carpathian marginal and Magura frontal thrusts, as well as on some faults that be long to the SRFZ.
We are convinced that the record of seismically-induced clast fracturing on one of major fault zones in the Outer Carpathians should lead to re vision of the hitherto-existing seismic risk as sessment of this region, and particularly of the city of Krakow and other urbanized areas, as well as the planned artificial water res er voir at Swinna Poreba.

• 出版日期2009