Preliminary Study: Density Layer Values Estimation of Volcano Hosted Geothermal Area at Tiris Village, Probolinggo Regency, East Java, Indonesia
Sukir Maryanto, Salman H. Siombone, Andre Prayogo, Tika Yulia, Rendi P.H. Sari
A preliminary study has been conducted using gravity method to estimate the volcano hosted geothermal system at Tiris, Probolinggo Regency, East Java. Gravimeter LaCoste & Romberg type G-1503 used for acquisition data which it collected in grid design with 100 meters per each datum. Complete Bouguer anomaly was obtained through gravity correction methods, then reduced into the flat plane and separated between regional anomalies and residual anomalies using upward continuation method. Complete Bouguer anomaly result had value ranged from 49–63 mGal and residual anomaly values ranged from -8.5–5.5 mGal. Subsurface structure identification for determining geothermal layer system was obtained by making three intersection lines (i.e AA’, B-B’ and C-C’) on the residual anomaly map and analyzing their cross-sections. Based on the modeling results of A-A’, BB’ and C-C’ cross-sections in terms of density values, it is estimated that the sub-surface rocks of the research area are composed by Lamongan volcano tuff-breccia rocks, Lamongan volcano breccia-lava rocks, Argopuro volcano andesitic-lava rocks, and old-Tengger andesitic-breccia rocks. The Argopuro volcano andesitic-lava rocks are suspected as the geothermal heat source because it volcanic activity is still detected. Furthermore, the Lamongan volcano breccia-lava suspected as
the geothermal reservoir where they have large porosity so that the water passes and heated easily.
Keywords: Tiris, Bouguer anomaly, density, geothermal system, gravity.
Ambient Noise Tomography for Determining the Velocity Model of Rayleigh Wave in Java Island, Indonesia
Muhajir Anshori, Sukir Maryanto, Tri Deni Rahman, Azwar Panshori
Ambient Noise Tomography had been applied to describe the Rayleigh wave group velocity model in the crust of Java Island, Indonesia. The collected seismic data consist of vertical component that recorded in January to December 2011 from 12 seismic stations at Indonesia Tsunami Early Warning System (INA TEWS) BMKG network Seismograph in Java Island. The waveform data processing was conducted from the preparation stage of daily waveform data, signal conditioning to signal cross correlation between paired stations that produced the empirical green function of the medium where the signal propagated. The estimated travel time of Rayleigh wave group for both periods of 5 s and 20 s were obtained from the time delay of the cross correlation. There were obtained by 36 and 22 traces respectively. The tomography process was conducted by using FMST v1.1 where forward and inverse modeling performed iteratively. The modeling result for the period of 5 s shown that the distribution of negative anomalies corresponded to volcanoes and Inter-Volcano plains which were Quarter-old. For period of 20 s, the western part of Java Island had a lower velocity anomaly than the eastern Java. This indicated that the tectonic activity of the western Java was more complex.
Keywords: tomography, ambient noise, crosscorrelation, Rayleigh.
Microseismicity of Blawan hydrothermal complex, Bondowoso, East Java, Indonesia
Peak Ground Acceleration (PGA), hypocentre, and epicentre of Blawan hydrothermal complex have been analysed in order to investigate its seismicity. PGA has been determined based on Fukushima-Tanaka method and the source location of microseismic estimated using particle motion method. PGA ranged between 0.095-0.323 g and tends to be higher in the formation that containing not compacted rocks. The seismic vulnerability index region indicated that the zone with high PGA also has a high seismic vulnerability index. This was because the rocks making up these zones were inclined soft and low-density rocks. For seismic sources around the area, epicentre and hypocentre, have estimated base on seismic particle motion method of single station. The stations used in this study were mobile stations identified as BL01, BL02, BL03, BL05, BL06, BL07 and BL08. The results of the analysis particle motion obtained 44 points epicentre and the depth of the sources about 15 – 110 meters below ground surface.
Development of Seismic Data Acquisition Based on MEMS Accelerometer MMA7361L
Amalia C. Nur’aidha, Didik R. Santoso, Sukir Maryanto
MEMS Accelerometer MMA7361L is an accelerometer-based sensor has been to develop for seismic acquisition system. The MMA7361L sensor has a linear frequency response to acceleration from 0Hz to 800Hz and works in three components. The signal response test has been done by the MMA7361L sensor compared with the L4C and SM-24 geophone-based sensors in the Laboratory of Volcanology and Geothermal, Cangar, Batu with providing vibrations at varying distances to get a signal response and frequency range of MMA7361L. The test results obtained MMA7361L sensor frequency range from 20Hz until 60Hz in three components work. Therefore, the MMA7361L sensor on this seismic data acquisition system has very low sensitivity.
Keywords : MEMS Accelerometer MMA7361L, seismic data acquisition, frequency, sensitivity.
Implementation of Town Watching and Development of Observatory for Community Education in Volcano Hazard Mitigation: study case at Kelud and Arjuno-Welirang volcanoes, East Java, Indonesia
Sukir Maryanto, Ahmad Nadhir, Didik R. Santoso
A Town Watching has been implemented at Kelud volcano region and an Observatory is being developed at Arjuno-Welirang Volcano Hosted Geothermal area in order to improve community education for volcano hazard mitigation in East Java, Indonesia. From the results shown that the level of participant’s interest was good because more than 75% expressed interest in the Town Watching implementation and 70% participants stated that they understand about the material presented at the event. All of the participants stated that the Town Watching was necessary and they hope that it could be done periodically. Almost 95% participants satisfied and 90% participants expected that similar town watching should be done in the future. In addition, an observatory of volcano was being developed at Arjuno-Welirang volcano complex in strengthening education in the field of volcano hosted geothermal. The observatory can be developed as part of pilot project in community education in that field. In the future, it can be integrated with town watching as a unity in education and research in the field of volcano hazard mitigation.