Imaging of upper crustal structure beneath East Java-Bali, Indonesia with ambient noise tomography

The complex geological structures in East Java and Bali provide important opportunities for natural resource exploitation, but also harbor perils associated with natural disasters. Such a condition makes the East Java region an important area for exploration of the subsurface seismic wave velocity structure, especially in its upper crust. We employed the ambient noise tomography method to image the upper crustal structure under this study area. We used seismic data recorded at 24 seismographs of BMKG spread over East Java and Bali. In addition, we installed 28 portable seismographs in East Java from April 2013 to January 2014 for 2–8 weeks, and we installed an additional 28 seismographs simultaneously throughout East Java from August 2015 to April 2016. We constructed inter-station Rayleigh wave Green’s functions through cross-correlations of the vertical component of seismic noise recordings at 1500 pairs of stations. We used the Neighborhood Algorithm to construct depth profiles of shear wave velocity (Vs). The main result obtained from this study is the thickness of sediment cover. East Java’s southern mountain zone is dominated by higher Vs, the Kendeng basin in the center is dominated by very low Vs, and the Rembang zone (to the North of Kendeng zone) is associated with medium Vs. The existence of structures with oil and gas potential in the Kendeng and Rembang zones can be identified by low Vs.The data used in this study were taken from BMKG (Free) and portable seismometers installed independently by the help of funding from the Australian Department of Foreign Affairs and Trade Grant 71982

Rancang Bangun Alat Pengamatan Gas Radon Menggunakan RN53 STK

Radon (Rn222) is a radioactive element derived from Uranium (U238) which emits alpha particles in its decay process. Detection of radon gas is important because it is not harmful to health. Besides being harmful to health, radon detection is also carried out to determine changes in radon gas related to seismic activity. The Meteorology, Climatology, and Geophysics Agency (BMKG) conducts observations of radon gas concentrations to determine changes in seismic activity. The design of the radon gas measurement instrument using the RN53 sensor is to monitor radon gas concentrations at the location and can be sent via the GSM network to the Thingspeak platform. The design of this instrument using the RN53 sensor has a correction of -92.90 Bq/m3, so it is necessary to make adjustments as well as calibration and comparisons again. The observations from the system are displayed on the LCD, stored on the microSD, and sent to Thingspeak

Pencitraan Struktur Kecepatan Gelombang Seismik Wilayah Pulau Sulawesi Menggunakan Metode Ambient Noise Tomography

Ambient Noise Tomography telah diterapkan untuk menggambarkan model kecepatan grup gelombang Rayleigh pada bagian kerak bumi Pulau Sulawesi. Data penelitian yang digunakan merupakan data waveform dalam format miniseed komponen vertikal seismograf broadband dari 25 stasiun jaringan INA TEWS BMKG yang tersebar di Pulau Sulawesi. Panjang data waveform adalah 3 bulan, yaitu bulan Juli 2016, Januari 2017, dan Agustus 2017. Pengolahan data waveform dilakukan mulai dari single data preparation, crosscorrelation dan stacking, analisis cross correlogram, pengukuran kurva dispersi, tomografi kecepatan dan yang terakhir adalah interpretasi hasil penelitian. Representasi metode Ambient Noise Tomography pada data rekaman seismik jaringan INA-TEWS BMKG di wilayah Pulau Sulawesi menghasilkan citra tomografi kecepatan grup gelombang Rayleigh (U) 3D untuk daerah Lengan Utara Pulau Sulawesi, Bagian Tengah Pulau Sulawesi, Lengan Selatan Pulau Sulawesi, Lengan Timur Pulau Sulawesi dan Lengan Tenggara Pulau Sulawesi yang secara umum berkorelasi dengan kondisi geologi daerah tersebut. Hasil tomografi yang diperoleh dari penelitian ini menunjukkan bahwa nilai kecepatan grup gelombang Rayleigh (U) di wilayah Pulau Sulawesi Sulawesi bervariasi dari 0.4 km/s hingga 4.8 km/s dan secara umum akan semakin tinggi seiring dengan bertambahnya periode atau dengan kata lain nilai kecepatan gelombang seismik yang diperoleh meningkat seiring dengan bertambahya kedalaman. Dari tomogram yang diperoleh teridentifikasi beberapa struktur geologi seperti cekungan, patahan, dan zona gunung api. Sesar-sesar yang berada di wilayah Pulau Sulawesi dengan jelas teridentifikasi pada tomogram yang direpresentasikan oleh batas antara kontras zona anomali kecepatan rendah dan zona anomali kecepatan tingg