Ground shear strain value based on microseismic data in Oebelo, Kupang NTT

Abstract

Information the ground shear strain in an area are very important. Quantitatively, this characteristic is reflected in the value of shear strain. This value provides an illustration of the ability of the soil layer to vibrate, stretch or shift even broken during an earthquake. The potential of vibrating and stretching of the soil is not only influenced by the magnitude and hypocenter but also the geological conditions of the local area. Geological characteristics in the form of dominant frequency values and amplification factors were obtained through the HVSR method using microseismic waves. The study was conducted in Oebelo, Kupang with a distribution of 52 points of microseismic measuring. Its parameters are used to calculate the seismic vulnerability index value and PGA value. These two values are used to determine the shear strain value at each measuring point. The results showed the magnitude of shear strain values was range from 1.5 × 10−2 to 1.6 × 10−1. The highest is located at coordinates 10.111280 S and 123.74180 E, while the area with the lowest at the coordinates 10.115780 S and 123.73960 E. Areas with shear strain values in the range 10−2 to 10−1 above, have dynamic properties are collapse, repeat-effects and speed-effects of loading. Phenomena that will occur are landslides, soil compaction and liquefaction during an earthquake. In the context of risk reduction, it is necessary to avoid areas with high shear strain values for human activities and infrastructure development.