Palu City is an active seismic area in Indonesia due to the very active Palu-Koro fault system. The development of the city area, therefore, must consider the risks induced by the seismic activities. The risk assessment has to be supported by information on subsurface characteristics. The aim of this study is to investigate the characteristics of the subsurface of the area by considering the value of V s30 (top 30 m shear-wave velocity). This parameter has been related to the estimation of the site's ground shaking during the occurrence of an earthquake. The measurements taken in the deep soil sediment include the microtremor array, using the spatial auto correlations (SPAC) method, as well as the site's dominant period measurement, using the horizontal-to-vertical spectral ratio (HVSR) method. All these parameters were local site parameters, which could be subsequently related to a description of the potential impact in an area near to the epicenter. The measurement of V s30 was conducted in collaboration between the Indonesian Agency for Meteorology, Climatology, and Geophysics (Badan Meteorologi, Klimatologi, dan Geofisika) (BMKG) and the University of Indonesia (Universitas Indonesia) (UI); the overall surveys included V s30 measurements at 44 sites, microtremor array surveys at 10 sites, and the dominant period measurements at 74 sites. The overall results indicated that there is a good correlation between V s30 and the dominant period. In general, Palu City is predominantly a class-D site, but the northwest part of the Palu area is a class-C site.

A 7.4 magnitude earthquake have strucked Donggala on September 28th 2018, followed by tsunami and liquefaction which hit Palu, Central Sulawesi, a few minutes later. This event had resulted in damage to buildings, and caused more than 2,000 people were killed and injured. Indonesia already have a building code in form of SNI 1726:2002 which had been updated to SNI 1726:2012. This paper analyses the hazard level caused by the 2018 Donggala earthquake compared to the existing design spectra, as mentioned in SNI 1726:2002 and SNI 1726:2012. A simple analysis was carried out by comparing Donggala earthquake’s acceleration response spectra with the existing design spectra, at the MPSI accelerograph station. The site class at MPSI station is hard soil (SC). The seismic hazard in Palu and Donggala refers to SNI 1726:2002 is included in the earthquake area 4. The maximum earthquake response factor for earthquake area 4 is about 0.6 for hard soil type (SC). The MPSI station recorded peak ground acceleration of Donggala earthquake around 0.14 g. The acceleration response spectra recorded at the MPSI station showed a peak value of around 0.71 g for the N component. This value is actually still below the design spectra referring to SNI 1726:2012, which the peak value is 0.88 g for SC, but, it exceeded the design spectra of SNI 1726:2002.

Lombok Island and its surrounding is an area that has a high seismicitys level because it is located in the Eastern Sunda Arc. Tectonically, Lombok Island located between the Indo-Australia plate collision zone with Eurasia in the south and the fult of the backarc Bali-Flores in the north. This research’s purposed to determine the distribution of vulnerability index and peak ground acceleration value are used to determine the GSS value, so mapping of potential damage areas could be done. The microtremor data taken on 32 observation points distributed in Lombok Island. Microtremor data is analysed using Horizontal to Vertical Spectral Ratio (HVSR) method to get seismic vulnerability index (Kg) and dominant period. Determination of Peak Ground Acceleration (PGA) value using data from the MASE Stasion measurement results based on earthquake events on August 5, 2018. Seismic vulnerability index and peak ground acceleration value are used to determine the GSS value. Determination of potential damage area using analysis of the dominant period, seismic vulnerability indexs and Ground Shear Strain values. The results of this research showed that seismic vulneribility index value in research area is about 0,029 sekon to 1,360 sekon, seismic vulneribility index value is about 0,56 to 189,92 and GSS value is about 2,52 x 10-5 to 8,46 x 10-3. The results show that the light damage dominated in East Lombok Districts, the moderate damage is on Mataram City and it dominated in West Lombok Districts. The heavy damage present in the most parts of West Lombok Districts.

Yogyakarta merupakan salah satu wilayah yang aktif gempabumi di Indonesia. Sumber gempabumi dapat berasal dari patahan lokal Opak di bagian timur ataupun zona subduksi pada bagian selatan Yogyakarta. Pembuatan peta mikrozonasi gempa sangat dibutuhkan untuk pertimbangan pembangunan infrastruktur atau bangunan yang tahan terhadap gempabumi. Upaya tersebut diharapkan dapat mengurangi dampak resiko yang mungkin ditimbulkan. Pada pertengahan tahun 2014 telah dilakukan pengukuran kecepatan gelombang geser (Vs30) di wilayah Yogyakarta khususnya wilayah Kabupaten Bantul dan Sleman. Pengukuran dilakukan terhadap 55 titik yang menyebar pada dua wilayah Kabupaten tersebut dengan jarak antar titik sekitar 1 sampai 5 km. Vs30 merupakan salah satu parameter yang digunakan dalam peta mikrozonasi. Pengukuran Vs30 dengan metode Multichannel Analysis of Surface Waves (MASW) menggunakan 24 geofon komponen vertikal dengan frekuensi 4.5 Hz. Nilai Vs30 memberikan informasi klasifikasi tanah permukaan sampai pada kedalaman 30 meter. Hasil interpretasi nilai Vs30 menunjukkan bahwa pusat kota yaitu Kotamadya Yogyakarta memiliki resiko amplifikasi gelombang yang relatif besar dengan nilai Vs30 berkisar antara 115-175 m/s. Pembangunan di wilayah ini sangat disarankan untuk memperhatikan aturan yang memenuhi standard sesuai rujukan SNI 1726-2012. Pada sisi lain, wilayah yang memiliki tanah permukaan klasifikasi padat dengan nilai rata-rata Vs30 antara 350-480 m/s adalah Kecamatan Kretek, Sanden, Pandak dan Bambanglipuro. Wilayah ini memiliki potensi untuk pelemahan atau atenuasi gelombang sehingga resiko kerusakan akibat gempabumi relatif lebih kecil.

In 2018, Lombok Island was hit by a major earthquake sequence. The Indonesia Meteorological, Climatological, and Geophysics Agency (BMKG) reported that the Lombok Island earthquake sequence started with an Mw 6.4 foreshock, followed by an Mw 6.8 main shock, aftershocks of Mw 5.8 and Mw 6.2, and a second mainshock of Mw 6.9 in the eastern part of Lombok. This study presents an investigation of strong motion characteristics using the Indonesia National Strong Motion Network (INSMN) data from two accelerometer stations, the MASE station (at Praya Lombok International Airport, Lombok Island, Vs30 = 770 m/s, SB site class) and TWSI station (in Sumbawa Island, Vs30 = 1152 m/s, SB site class). Signal analysis techniques using a power spectrum via fast Fourier transform, wavelet transform and horizontal-to-vertical spectral ratio (HVSR) have been applied in this study. There are significant differences in the results (e.g., predominant frequencies, wavelets, H/V ratios, and frequencies at peak H/V ratio) for the MASE and TWSI stations, highlighting the importance of actual Vs30 profiles and the limitation of the site class system in providing necessary predictive information. The variation of the peak ground acceleration (PGA) values and the spectral amplitudes could only be explained by hypothesizing the effect of the volcanic structure of Mount Rinjani on the strong motion waveforms.