Poisson's ratio analysis (Vp/Vs) on volcanoes and geothermal potential areas in Central Java using tomography travel time method of grid search relocation hypocenter

Raharjo, Wiji; Palupi, Indriati Retno; Nurdian, Setyo Wahyu; Giamboro, Wrego Seno; Soesilo, Joko

doi:10.1088/1742-6596/776/1/012114

Cited by 5 publications

(3 citation statements)

References 2 publications

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“…The distribution pattern of Vp and Vs values is relatively identical, the value is increasing as depth, there are striking differences values on the southern and northern parts. The distribution of Vp/Vs values that pass through hot springs is 1.8, Vp/Vs values illustrate the elasticity properties of rocks [12] and correlated with pore fluid pressure [13]. according to the result of [13] that the combination of high Vp, low Vs, and high Vp/Vs can be interpreted as rock fluid-saturated, in this study the combination is shown below HS-02, it reflects the potential area.…”

Section: Results and Analysissupporting

confidence: 52%

Delineation of Geothermal Manifestation in Sangubanyu Area Based on Microtremor HVSR Method

2019

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The aims of this study is to describe the distribution of P wave velocity and S wave velocity value and Vp/Vs ratio based on microtremor HVSR method and its relationship with the appearance of hot spring at Sangubanyu Village. Geothermal manifestations in the Sangubanyu area are located in Bawang sub-district, Batang regency, and Plantungan sub-district, Kendal regency, Central Java province. HVSR method is used to process microtremor data which produces the dominant frequency value and amplification factor then do inversion on the H/V curve to get the value of the Vp and Vs. The results of the microtremor HVSR processing obtained the distribution of the dominant frequency values in the study area between 0.62 to 0.73 Hz and amplification factor values 1.09 to 1.39, the inversion results on the H/V curve obtained the distribution of Vp values between 131.76 m/s to 2181.19 m/s, Vs values between 76.61 to 1129.42 m/s, Vp/Vs ratio 1.64 – 3.35. Based on the results of the analysis and wave velocity interpretation, the subsurface structure of manifestation area of Sangubanyu is composed of tuffaceous sandstone and volcanic breccia, the normal faults with southern blocks relatively downthrown, that cause the appearance of hot springs.

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Section: Results and Analysissupporting

confidence: 52%

Delineation of Geothermal Manifestation in Sangubanyu Area Based on Microtremor HVSR Method

2019

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“…Titik potensi panas bumi tersebut diduga merupakan sistem panas bumi non magmatik atau sumber panas bukan berasal dari aktivitas vulkanik (Direktorat Panas Bumi, 2017). Hal ini juga selaras dengan hasil studi analisis Vp/Vs yang menyatakan bahwa sumber panas bumi Cipari tidak berkorelasi dengan sumber panas bumi vulkanik terdekat, yaitu titik potensi panas bumi Guci dan Gunung Slamet (Raharjo et al, 2016). Potensi panas bumi di Cipari memiliki kenampakan dengan adanya mata air bersuhu sekitar 50°C dan suhu reservoir sekitar 70°C yang termasuk digolongkan dalam kategori temperatur rendah.…”

Section: Pendahuluanunclassified

Analisis Data Gravitasi Untuk Identifikasi Struktur Bawah Permukaan Daerah Potensi Panas Bumi Cipari

Agustin

Wibawa

2022

Jambura Geosci. Rev.

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Geothermal prospect in Cipari has been shown by spring who has a temperature of about 50°C and is categorized as a low temperature. The presence of spring on Cipari earth's surface is an indication of geothermal structures' existence on the surface and a geothermal system below the surface. Geophysical methods can be used for subsurface structures identification, one of them is the density method with gravity data. This study has an objective to identify the subsurface structures in Cipari geothermal potential area using GGMPlus gravity data. Terrain and Bouguer corrections were used to obtain Complete Bouguer Anomaly (CBA). Separation of regional and residual anomalies using Butterwoth and Bandpass filters. The rock contact boundary was obtained by the FHD method and geological structures such as faults were obtained by the SVD method. FHD and SVD results were used as information for 2D forward modeling. The ABL map shows anomalous contrasts in areas that have rock contacts and geological faults. The high anomaly in the center of the study area indicates the Cipari anticline. Data processing and analysis concluded that the area around the Cipari hot spring has anticline, several rock contacts, and normal fault structures. The fault in the study area is part of the geothermal system which is confirmed by GGMPlus data.

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“…It is a value between -1 and +0.5. Therefore (ν) is a function of the V p /V s ratio (Raharjo et al, 2016;Stein & Wysession, 2009) expressed below in Eq. 2.3):…”

Section: Vp/vs Ratios and Saturationmentioning

confidence: 99%

Comparing Theoretical With Measured Seismic Anisotropy in the Central Taupo Volcanic Zone

Jylhankangas

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Geothermal resources using high-enthalpy supercritical fluids (374◦C and 22.1 MPa for pure water) have the potential to generate up to ten times more electricity than conventional high-temperature geothermal resources. In the Taupo Volcanic Zone (TVZ), supercritical geothermal reservoirs may exist at 4 km in greywacke basement rocks, deeper than currently drilled depths (3.2 km). Finding permeable fractured zones is crucial for exploring supercritical resources.Shear wave splitting (SWS) is proposed as a supporting method to map deep fractured zones. SWS has been previously used to determine the dominant fracture alignments, fluid saturation and anisotropy response to stress variations with the fluid injections at the Rotokawa and Ngatamariki geothermal fields (TVZ), but uncertainties remain on the fractured rock parameters used in the inversion of earthquake data. This thesis combines forward modelling of elastic media (fractured rocks) and synthetic SWS using the MATLAB Seismic Anisotropy Toolkit (MSAT) to test the reliability of SWS observations in predicting fractured rock parameters and to validate SWS as a geothermal exploration method.Firstly, we investigate the SWS of different types of fracture infills and rock parameters in numerical fracture networks. From ten parameters, only crack density per unit volume and the orientations of the fractures (strike and dip magnitude) significantly impact S-wave anisotropy. The difference in anisotropy caused by fractures filled with conventional or supercritical geothermal fluids is negligible and would not be discernible in real data.Secondly, we seek the best rock parameters that fit the SWS observations at the Rotokawa and Ngatamariki geothermal fields measured at 42 stations. We model the effect of two fracture sets steeply dipping and striking NE-SW and N-S as documented from borehole images. The best fits to Shear wave polarisation observations are obtained with: • At Ngatamariki, dominant fracture set 205/NW/60 (strike/dip direction/dip) i and secondary fracture set 000/E/60, total crack density of 4.5%; • At Rotokawa, dominant fracture set 065/SE/70 and secondary set 000/E/60, total crack density of 2.5%.This work provides a framework to map fracture orientations and densities using shear-wave splitting of natural seismicity. This non-invasive method can help mapping zones that are sufficiently fractured to host geothermal resources prior to drilling. Identifying zones where fluids are at supercritical conditions still requires other methods.

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Poisson's ratio analysis (Vp/Vs) on volcanoes and geothermal potential areas in Central Java using tomography travel time method of grid search relocation hypocenter

Cited by 5 publications

References 2 publications

Delineation of Geothermal Manifestation in Sangubanyu Area Based on Microtremor HVSR Method

Delineation of Geothermal Manifestation in Sangubanyu Area Based on Microtremor HVSR Method

Analisis Data Gravitasi Untuk Identifikasi Struktur Bawah Permukaan Daerah Potensi Panas Bumi Cipari

Comparing Theoretical With Measured Seismic Anisotropy in the Central Taupo Volcanic Zone

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