A Comparison on Efficiency of Triangular and Orthogonal Arrays in Determination of Shear Wave Velocity Profile of the Layers Close to the Earth Surface using F-K Method

In order to assess and compare efficiency of triangular and orthogonal arrays in identification of subsurface structure specifications up to a depth of 50 meters using microtremor waves by F-K method, two triangular and orthogonal arrays with 13 and 12 stations (which included some sub-arrays), respectively, were studied in a site located in north of Iran and besides the Caspian Sea called Kalarabad. Data acquisition in these arrays was carried out using three-component seismographs with minimum and maximum distance of 5 meters and 70 meters, respectively, for at least 18 continuous hours. In the mentioned site, dominant layering was saturated and poorly graded sandstone and shear wave velocity profile was formerly determined for a depth up to 50 meters by Down Hole method. Natural and dominant frequency of the site was obtained as much as 0.33 by H/V analyses. The dispersion curves obtained through processing each of subarrays were extracted and then compared with the dispersion curve obtained through shear wave velocity profile of Down Hole. This comparison indicated better efficiency of orthogonal arrays in the mentioned site. Also, azimuth direction of wave propagation was assessed in this site and the corresponding effects on subsurface structure identifiable ranges were studied in triangular and orthogonal arrays along with theoretical response for each form.