Local geological condition and site dynamic parameters especially shear wave velocity (Vs) are of great importance in designing safe structures and prohibition or reduction earthquake disasters particularly in populated cities. Iranian eastern cities, located on young sediments and having moderate to high seismicity potential, have been subjected to seismic hazards and have been involved in pertinent studies. In this regard, in the absence of adequate information for Khash area, SE Iran, a reconnaissance campaign—including geological, geotechnical and seismic downhole surveys— was carried out, to characterize the site and to provide a setting for detailed microtremors surveys aimed at assessing site effects and Vs structure. Accordingly, site geology was studied. Using seismic downhole surveys Vs structures were obtained in 6 boreholes based of which the ground was classified as class C and II in terms of the NEHRP provisions and Iranian code of practice, respectively. Microtremors were measured at 85 stations and were analyzed using H/V technique. Three different shapes of the H/V curves were recognized and their spatial distributions were mapped. The analysis shows a resonance period range of 0.4-1.54 s and a quasi-amplitude range of 1.8 to 7.0. It is shown that the Vs30-based classes of the site differ from the period-based classes, indicating that herein the Vs30 is not sufficient for site amplification, as mentioned by other authors. By inverting H/V curves, we obtained 11 1-D velocity models using ModelHVSR program. These Vs models that are related to the sites having rather high amplitudes and clear peaked curves are comparable to what obtained by downholes.

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