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Ultrasonic techniques are a simple, cost-effective, portable and non-destructive approach for evaluating the uniaxial compressive strength (UCS) of rocks. However, there are a number of factors affecting the ultrasonic pulse velocity ( V p ) values. The main factors controlling the reliability of the method are surface irregularities of rock, micro-cracks and discontinuities, moisture content and porosity. To provide high prediction performances, data obtained from simple test methods are considered in combination to predict the mechanical properties of intact rocks. In this context, the use of both the V p and Schmidt hammer rebound provides a better estimate of the UCS and minimizes the influence of the factors affecting the two techniques when they are used separately. The scope of this study is to assess the reliability and accuracy of the combined method in rock mechanics applications requiring the in situ determination of the UCS. The study material consists of various rock blocks of different strengths. The empirical relationships relating the V p and rebound number (RN) were investigated using simple and multiple regression analysis. It was found that the combined method provides better estimates for UCS than V p and RN separately. This method is proposed to indirectly determine the UCS of intact rocks.

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The seismic hazard for the Lake Van basin is computed using a probabilistic approach, along with the earthquake data from 1907 to present. The spatial distribution of seismic events between the longitudes of 41-45°and the latitudes of 37.5-40°, which encompasses the region, indicates distinct seismic zones. The positions of these zones are well aligned with the known tectonic features such as the Tutak-Ç aldıran fault zone, the Ö zalp fault zone, the Gevaş fault zone, the Bitlis fault zone and Karlıova junction where the North Anatolian fault zone and East Anatolian fault zone meet. These faults are known to have generated major earthquakes which strongly affected cities and towns such as Van, Muş, Bitlis, Ö zalp, Muradiye, Ç aldıran, Erciş, Adilcevaz, Ahlat, Tatvan, Gevaş and Gürpınar. The recurrence intervals of M s C 4 earthquakes were evaluated in order to obtain the parameters of the Gutenberg-Richter measurements for seismic zones. More importantly, iso-acceleration maps of the basin were produced with a grid interval of 0.05 degrees. These maps are developed for 100-and 475-year return periods, utilizing the domestic attenuation relationships. A computer program called Sistehan II was utilized to generate these maps.