Wave Velocity Model Research Articles

Method of automated extracting dispersion curves based on time-frequency distribution of seismic data

This paper discusses examples of testing a new implementation of the method of multi-channel surface wave analysis on synthetic data computed for elastic media with complex boundary geometry. The new implementation of the method includes developed algorithms for noise-resistant spectral analysis based on time-frequency domain filtering of seismograms and inversion of dispersion curves of phase velocities based on determination of ranges of possible transverse wave velocity models and application of artificial neural networks. Based on the results of synthetic data processing, the accuracy, lateral resolution limitations and applicability limits of the method under consideration are evaluated.

Shallow three-dimensional shear wave velocity model for the Mexico City Basin

In this study, a simplified shallow three-dimensional shear wave velocity (Vs) model is presented for the Mexico City Basin. To this end, previous studies were carefully reviewed to assemble a database of Vs and site period measurements for the region. The new site period measurements obtained at the western edge of the Basin were compared to the existing 2004 Complementary Technical Standards of Mexico site period nominal map, (NTC, 2004) the Lermo et al. (2020) site period map, and Design Seismic Actions System (SASID), 2020 site period predictions. Each site period prediction method was shown to have differences with respect to the new measurements along the western edge of the Basin. However, there was no bias for the prediction methods with the Lermo et al. (2020) and SASID predictions, demonstrating less error between the measured values than the NTC (2004) predictions. To develop the three-dimensional Vs model, the shallow (top 60 m) subsurface was divided into five generalized soil layers. The site period was used as the only input for the three-dimensional Vs model to simplify and maximize the model’s applicability. The performance of the model was assessed by comparing the measured and predicted Vs profiles. Overall, the three-dimensional Vs model developed in this study is a valuable tool that can be used along with geophysical estimates of deeper structure for ground motion modeling and preliminary site response studies along with other benefits to the seismic resiliency of the region.

Passive seismic tomography for 3D imaging of the subsurface in a tunnel area

This study aims to provide decision support for future measures to be taken regarding 2 tunnels using high-resolution 3D imaging of the subsurface. This project involves a more comprehensive risk analysis than localized tests, such as geotechnical surveys, and a more precise characterization of the subsoil at the tunnel entrance for approximately 200 meters. To address this issue, a 3D passive seismic tomography was conducted using a network installed on the surface of the study area and another in the tunnels to better analyze the subsurface beneath the tunnels. The 3D shear wave velocity model allowed the identification and delineation of risk zones and the estimation of risk levels based on the analysis of Vs (shear wave velocity) contrasts and their correlation with borehole data.

Topography‐Incorporated Adjoint‐State Surface Wave Traveltime Tomography: Method and a Case Study in Hawaii

AbstractIn this study we recast surface wave traveltime tomography as an inverse problem constrained by an eikonal equation and solve it using the efficient adjoint‐state method. Specifically, recognizing that large topographic variations and high surface wave frequencies can make the topographic effect too significant to ignore, we employ an elliptically anisotropic eikonal equation to describe the traveltime fields of surface waves on undulated topography. The sensitivity kernel of the traveltime objective function with respect to shear wave velocity is derived using the adjoint‐state method. As a result, the newly developed method is inherently applicable to any study regions, whether with or without significant topographic variations. Hawaii is one of the most seismically and magmatically active regions. However, its significant topographic variations have made it less accurate to investigate using conventional surface wave traveltime tomography methods. To tackle this problem, we applied our new method to invert ambient noise Rayleigh wave phase traveltimes and construct a 3D shear wave velocity model. Our results reveal features that are consistent with geological structures and previous tomography results, including high velocities below Mauna Loa Volcano and Kilauea Volcano, and low velocities beneath the Hilina Fault Zone. Additionally, our model reveals a high‐velocity anomaly to the South of Hualalai's summit, which may be related to a buried rift zone. Our findings further demonstrate that including topography can lead to a correction of up to 0.8% in the shear wave velocity model of Hawaii, an island spanning approximately 100 km with volcanoes reaching elevations exceeding 4 km.

Imaging high-resolution 3D shallow crustal structure by ambient noise method in the Shiziyang Waterway area, Guangzhou, South China

The Shiziyang Waterway, located in the northern continental margin of the South China Sea, has developed a complex fault system owing to the coupling action of the oceanic crust and continental crust. However, the geological structure in the shallow crust beneath the Shiziyang Waterway and the relationship between faults and waterway development are still unclear, resulting in difficulty in assessing the earthquake risk to the surrounding cities. In this study, based on a high-density short-period seismic array that was recently deployed around the Shiziyang Waterway, a high-resolution shear wave velocity model is inverted to as shallow as 4 km by the ambient noise tomography method. The results showed that at depths ranging from 0.2 to 4 km, three sets of low-velocity zones (LVZs), trending east–west, northeast, and northwest, are revealed, which are speculated to be the Shougouling fault (SGLF), Xinhui-Shiqiao fault (XSF), and Shiziyang fault bundle (SZYFb), respectively. The shear-wave velocity anomalies illustrate that the SGLF stopped extending east at the north endpoint of the Wenchong-Zhujiangkou fault (WZF). The two-stage differential vertical movements of the WZF, Nangang-Humen fault (NHF), and Hualong-Haioudao fault (HHF) dominated the opening of the Shiziyang Waterway. This study provides new seismological evidence of the opening process for the Shiziyang Waterway and reveals that internal fault activity dominated the development and evolution of the Pearl River Delta.

A Preliminary Results: Study of Crustal Structure in Cimandiri Fault Based on Teleseismic Receiver Function Analysis

West Java is one of the regions in Indonesia that has a complex geological structure caused by plate subduction in the south of Java Island. This resulted the formation structure of the main faults in West Java, including the Cimandiri Fault. The high level of seismicity on the Cimandiri Fault is interesting to be further researched to understand the structure of the Earth crustal, such as variations depth of the Moho layer and the determination of local velocity models of P and S waves. This study used receiver function analysis from teleseismic earthquake data with an epicentral distance of 30°-90° from the station location and magnitude ≥ 6. This study used 3 seismic stations belonging to the Meteorological, Climatological, and Geophysical Agency (BMKG) close to the Cimandiri Fault which are Sukabumi station (SKJI), Warung Kiara (WSJM), and Sukaraja (SSJM). The depth of the Moho layer at SKJI station is 34-36 km, WSJM station is 28-30 km, and SSJM station is 29-31 km which is located close to the segment from the Cimandiri Fault. A negative phase or decrease in speed was observed at the SKJI and WSJM stations which is estimated to come from the Cimandiri Fault structure which is at a depth of 17-19 km. Furthermore, the P wave velocity model at the three stations is at an interval of 7.6-8.6 km/s and the S wave velocity model is at an interval of 4.2-4.8 km/s.

The Crustal Magmatic Structure Beneath the Denali Volcanic Gap Imaged by a Dense Linear Seismic Array

AbstractThe crustal structure in south‐central Alaska has been influenced by terrane accretion, flat slab subduction, and a modern strike‐slip fault system. Within the active subduction system, the presence of the Denali Volcanic Gap (DVG), a ∼400 km region separating the active volcanism of the Aleutian Arc to the west and the Wrangell volcanoes to the east, remains enigmatic. To better understand the regional tectonics and the nature of the volcanic gap, we deployed a month‐long north‐south linear geophone array of 306 stations with an interstation distance of 1 km across the Alaska Range. By calculating multi‐component noise cross‐correlation and jointly inverting Rayleigh wave phase velocity and ellipticity across the array, we construct a 2‐D shear wave velocity model along the transect down to ∼16 km depth. In the shallow crust, we observe low‐velocity structures associated with sedimentary basins and image the Denali fault as a narrow localized low‐velocity anomaly extending to at least 12 km depth. About 12 km, below the fold and thrust fault system in the northern flank of the Alaska Range, we observe a prominent low‐velocity zone with more than 15% velocity reduction. Our velocity model is consistent with known geological features and reveals a previously unknown low‐velocity zone that we interpret as a magmatic feature. Based on this feature's spatial relationship to the Buzzard Creek and Jumbo Dome volcanoes and the location above the subducting Pacific Plate, we interpret the low‐velocity zone as a previously unknown subduction‐related crustal magma reservoir located beneath the DVG.

Geodynamic evolution of north-east Algerian basin: 3D velocity model Reveals high-temperature flow

By utilizing a two-station technique to extract Rayleigh wave phase velocity curves from 10 to 200 s of teleseismic events recorded by 12 broadband stations installed in northeastern Algeria, Tunisia, Sardinia, and Menorca island, we present a 3D shear wave velocity (Vs) model of the crust and upper mantle beneath the North-East Algerian Basin from 50 to 400 km depth. To estimate the 1D Vs-structures at each node of the two-station paths, which are each partitioned into 10 points, the extracted experimental Rayleigh wave phase velocity curves were inverted. According to the findings, there are two primary parallel high- and low-velocity bodies in the same region that are spreading in NE-SW direction. These bodies are largely located beneath the Algerian offshore in the north and extend to the Tell belt in Algeria with similar geometry. The high shear wave velocity body is at 200 and 350 km deep with Vs between 5 and 6 km/s, while the low-velocity body is at 50 and 100 km depth with Vs between 3 and 4 km/s. This opposition in velocity with similar geometry is explained by a high-temperature flow induced in the upper mantle caused by a subducting lithosphere of high-velocity penetration, which resulted in a concentrated low-velocity body between 50 and 100 km into the African mantle as a result of the convergence of the Africa-European plates. This high-velocity entity may be created by the oceanic lithosphere subducting.

Generalization of disturbance wave velocity of vertical annular flow considering entrained droplets effect

A full knowledge of the interfacial effect on disturbance wave is vital for accurately predicting disturbance wave velocity in annular flow. However, almost all of the existing disturbance wave velocity models do not ponder the droplet-film mass transfer, which largely limits the applicable scope and prediction accuracy of the model. This article leads into the entrained droplets effect to the interfacial shear modeling, proposing a new disturbance wave velocity model with a widely applied range. The effects of entrainment and liquid film thickness on the characteristics of the gas core mixture (bulk density and velocity) were included, and the mean velocity of the liquid film surface was introduced in the modelling. For the verifying experiments, an annular flow loop with film metering device and electrode sensor was developed, and the entrainment and liquid film thickness were also modelled for the convenience of usage in cases without raw measured data. The new developed disturbance wave velocity model collapses the experiments corresponding to all entrained conditions well within ± 5.0% deviation for an 85.2% confidence interval. The comparative analysis with the existing empirical correlations confirms the critical role of entrained droplets on the disturbance wave velocity. The scalability and wide scope of application were further validated by the open data in the literature, and finally, practical suggestions were given for the disturbance wave velocity prediction on various pressure and pipe diameter conditions.

3-D crustal shear wave velocity and azimuthally anisotropic structure of the Pearl River Delta onshore-offshore area and its tectonic implications

The Pearl River Delta (PRD) onshore-offshore area lies in the transition zone between South China and northern continental margin of the South China Sea. To better understand the tectonic and deformation patterns at depth, we developed a 3-D high-resolution crustal shear wave velocity (Vs) and azimuthal anisotropy model by ambient noise tomography in this region. The data sets comprise ∼30 days of seismic ambient noise recorded by 124 land seismic stations and 28 Ocean Bottom Seismometers (OBS). Our results reveal a significant lateral contrast in azimuthal anisotropy in the crust. The fast axes of the azimuthal anisotropy in land show an approximately NW-SE direction, which may be mainly controlled by the regional stress field. In the offshore PRD, however, the fast axes of anisotropy strike nearly in the NE-SW direction, likely dominated by the shearing of the littoral fault zone. Combined with other previous results, the anisotropic model reveals three major crustal deformation processes in this region since the Yanshanian. Furthermore, an upper-middle crustal frozen mafic magma chamber with high Vs (∼3.85–4.0 km/s) is imaged beneath Shenzhen, Zhuhai, and Hong Kong. It is interpreted as a source of intense magmatic activities in and around Hong Kong during the late Mesozoic. Our new model provides important constraints for understanding the crustal architecture and the multistage deformation processes in and around the PRD onshore-offshore area.

Transdimensional ambient-noise surface wave tomography of the Reykjanes Peninsula, SW Iceland

SUMMARY Ambient noise seismic tomography has proven to be an effective tool for subsurface imaging, particularly in volcanic regions such as the Reykjanes Peninsula (RP), SW Iceland, where ambient seismic noise is ideal with isotropic illumination. The primary purpose of this study is to obtain a reliable shear wave velocity model of the RP, to get a better understanding of the subsurface structure of the RP and how it relates to other geoscientific results. This is the first tomographic model of the RP which is based on both on- and off-shore seismic stations. We use the ambient seismic noise data and apply a novel algorithm called one-step 3-D transdimensional tomography. The main geological structures in the study area (i.e. covered by seismic stations) are the four NE–SW trending volcanic systems, orientated highly oblique to the plate spreading on the RP. These are from west to east; Reykjanes, Eldvörp-Svartsengi, Fagradalsfjall and Krýsuvík, of which all except Fagradalsfjall host a known high-temperature geothermal field. Using surface waves retrieved from ambient noise recordings, we recovered a 3-D model of shear wave velocity. We observe low-velocity anomalies below these known high-temperature fields. The observed low-velocity anomalies below Reykjanes and Eldvörp-Svartsengi are significant but relatively small. The low-velocity anomaly observed below Krýsuvík is both larger and stronger, oriented near-perpendicular to the volcanic system, and coinciding well with a previously found low-resistivity anomaly. A low-velocity anomaly in the depth range of 5–8 km extends horizontally along the whole RP, but below the high-temperature fields, the onset of the velocity decrease is shallower, at around 3 km depth. This is in good agreement with the brittle–ductile transition zone on the RP. In considerably greater detail, our results confirm previous tomographic models obtained in the area. This study demonstrates the potential of the entirely data-driven, one-step 3-D transdimensional ambient noise tomography as a routine tomography tool and a complementary seismological tool for geothermal exploration, providing an enhanced understanding of the upper crustal structure of the RP.

Rayleigh wave dispersion-based estimation of high-resolution 2D-subsurface shear wave velocity models: application of updated approaches

Rayleigh wave dispersion-based estimation of high-resolution 2D-subsurface shear wave velocity models: application of updated approaches

Basin Structure for Earthquake Ground Motion Estimates in Urban Los Angeles Mapped with Nodal Receiver Functions

We constrained sedimentary basin structure using a nodal seismic array consisting of ten dense lines that overlie multiple basins in the northern Los Angeles area. The dense array consists of 758 seismic nodes, spaced ~250–300 m apart along linear transects, that recorded ground motions for 30–35 days. We applied the receiver function (RF) technique to 16 teleseismic events to investigate basin structure. Primary basin-converted phases were identified in the RFs. A shear wave velocity model produced in a separate study using the same dataset was incorporated to convert the basin time arrivals to depth. The deepest part of the San Bernardino basin was identified near the Loma Linda fault at a depth of 2.4 km. Basin depths identified at pierce points for separate events reveal lateral changes in basin depth across distances of ~2–3 km near individual stations. A significant change in basin depth was identified within a small distance of ~4 km near the San Jacinto fault. The San Gabriel basin exhibited the largest basin depths of all three basins, with a maximum depth of 4.2 km. The high lateral resolution from the dense array helped to reveal more continuous structures and reduce uncertainties in the RFs interpretation. We discovered a more complex basin structure than previously identified. Our findings show that the basins’ core areas are not the deepest, and significant changes in basin depth were observed near some faults, including the San Jacinto fault, Fontana fault, Red Hill fault and Indian Hill fault.

Crustal and uppermost mantle structure near the Gloria Fault, North Atlantic, from ocean bottom seismometer surface wave observations

SUMMARY In this work, we present both 1-D and 3-D shear wave velocity (Vs) models of the oceanic crust and uppermost mantle below the Deep OCean Test ARray area, located ∼ 70 km north of the central section of the Gloria Fault, in the eastern North-Atlantic Ocean. The velocity models are inferred from the dispersion of surface waves recorded on ocean bottom seismometers. Dispersion measurements are obtained from the analysis of ambient seismic noise at short periods (< 14 s) and teleseismic surface waves at long periods (> 14 s) using the two-station method. The 1-D Vs model is inferred from the joint inversion of Rayleigh wave phase velocities and Love wave group and phase velocities. The 3-D tomographic model is obtained by inversion of 2-D Love wave group velocity maps as a function of depth, further constrained by the average of Love wave phase velocities obtained from ambient noise (4–9 s) and the average Rayleigh and Love wave phase velocities calculated from teleseismic data (14–44 s). The 1-D Vs model shows a sediment layer with a low velocity of 1.05 km s−1, similar to previous studies in the region. Below the sediments, we find an oceanic crust with velocities ranging from 3.3 to 4.5 km s−1. The model reaches an unusually high velocity of 4.9 km s−1 in a 20 km thick layer at depths between 16 and 36 km. We interpret this fast velocity layer as indicative of the presence of harzburgite, a residue of enhanced melting that might have been formed by the proximity between the Mid-Atlantic Ridge and the Azores mantle plume. At greater depths the velocity decreases, forming a low-velocity zone that reaches a minimum at ∼ 70 km depth, which we interpret as the maximum depth for the lithosphere–asthenosphere boundary. The 3-D model shows a structure that is mostly horizontally layered, with Vs isocontours at 3.5–4.5 km s−1 highlighting oscillations of the crustal structure with wavelengths of ∼25–30 km. These oscillations may be due to changes in the rate of mantle upwelling and magma supply rate.

Seismic structure of the Eastern European crust and upper mantle from probabilistic ambient noise tomography

The Eastern European lithosphere is a natural laboratory to study continental formation and evolution through time, comprising Archean continental remnants, Proterozoic rifts and belts, and younger accreted terranes. We investigate the seismic structure of the East European Craton (EEC) crust and uppermost mantle, and the transition from Precambrian to Phanerozoic Europe across the Trans European Suture Zone (TESZ) using probabilistic transdimensional ambient noise tomography. We cross-correlate noise recorded at broadband seismic stations from Eastern, Northern, and Central Europe, remove earthquake signals using continuous wavelet transform, and extract Rayleigh wave phase velocity dispersion curves. We invert these for the highest resolution shear wave velocity model of the Eastern European lithosphere to date, using Markov chain Monte Carlo Bayesian inversion. Our shear wave velocity model exhibits spatial correlation with major tectonic units and bears similarities with active seismic survey profiles in terms of seismic velocity patterns and main discontinuities. The crust thickens across the TESZ boundary and the mantle is seismically faster than beneath younger terranes, consistent with a less dense Precambrian lithosphere in the EEC. The crust and lithosphere beneath the Pannonian region is hyper-extended but the adjacent Transylvanian basin crust shows significant heterogeneity. The Precambrian building blocks of the EEC exhibit contrasting seismic fabrics. The Baltic orogens of Fennoscandia are underlain by uniform crust with a flat Moho, while Sarmatia shows alternating high and low velocity layers and a regional south-dipping crustal boundary from beneath the Ukrainian Shield towards the Crimean Peninsula. The last observation supports a geodynamic style driven by horizontal rather than vertical tectonics, with fundamental implications for the formation and evolution of early continents.

Seismic ambient noise imaging above an underground mine: An example from Boliden Tara Mines, Ireland

We use a passive seismic data set recorded from June 2017 to July 2018 by twenty-one stations deployed in a five by five km grid to the south-west of the Boliden Tara Mines orebody (Eastern Ireland) to image the shallower part of the Carboniferous rock units. We cross-correlate one year of ambient noise between all station pairs to generate cross-correlation functions that are rich in surface waves. Then we investigate the locations of the noise sources by applying f-k cross-correlation beamforming. We find two persistent noise sources associated with oceanic microseisms and a cluster of anthropogenic activities, respectively. We undertake dispersion analysis to extract group velocity measurements in the 1–9 Hz band that we invert using the fast marching method to create Rayleigh wave velocity maps. This is followed by a wavelet-based sparsity constrained tomographic method to produce a 3-D shear wave velocity model down to 800 metres. The results highlight low and high-velocity anomalies related to the structural and stratigraphic heterogeneity within the Upper Dark limestone formation. In addition, the velocity gradient of our model agrees with the sonic log velocity profile available adjacent to the study area, suggesting that this sparse network can be used to obtain reliable broad-scale information and could also guide the design phase of more expensive and involved experiments, such as active seismic reflection imaging.

Porosities-dependent wave propagation in bi-directional functionally graded cantilever beam with higher-order shear model

The contribution provided in this paper is to investigate the dynamic response of bidirectional graded material beams with porosities. Higher order shear deformation beam theory for wave propagation in porous functionally graded cantilevered beam are developed, taking into account the bidirectional distribution, which is mainly represented in the density and the Young’s modulus. The material properties of the porous FG beam are graded through the thickness and width using a power law distribution. The governing equations of the wave propagation in the porous FG beam are derived by employing the Hamilton’s principle. The analytic dispersion relation of the bidirectional porous FG beam is obtained by solving an eigenvalue problem. Two porosities models approximating the even and uneven distributions of porosity are considered. The results obtained for bidirectional FG beam were compared with those reported in the literature, and the results were very agreement. The effects of the volume fraction distributions, the number of wave propagation, various parameters and the porosity type on dynamic of functionally graded beam are discussed in details. The numerical results show that the power law index, number of wave, wave velocity, and porosity distribution model affect the dynamic behavior of the beam significantly. The results show that the uneven porosity predicts higher natural frequencies than the even porosity.

Geophysical Subsoil Characterization and Modeling Using Cluster Analysis for Seismic Microzonation Purposes

In the municipality of Enna, 80 HVSR measurements were performed, and some of these were combined with MASW seismic measurements, which made it possible to constrain the data inversion and obtain significant shear wave velocity models. A reconstruction of the depth of the seismic bedrock was performed for the whole territory, showing different depths for the higher and lower areas, as evidenced also by the Vseq parameter map. The frequency peaks identified in the H/V curve were analyzed through a cluster analysis algorithm to evaluate similarities that allow these peaks to be divided according to their stratigraphic origin. A non-hierarchical analysis algorithm modified in such a way as to avoid any a priori choice that could influence the partition has been used. The cluster analysis made it possible to divide the frequency peaks into five groupings, each of which was then associated with a seismic discontinuity, according to the geological contacts expected in the subsoil. Finally, the inversion of the data made it possible to reconstruct the geometries of these geological contact surfaces and to reconstruct a 3D model of the subsoil, which agrees well with the surface geology of the area.

Probabilistic shear wave velocity model based on downhole test database for Apennine flysch formations

Defining a reference shear wave velocity profile (Vs) is crucial for seismic-hazard assessment and seismic response analysis. However, selecting a reference velocity profile is not straightforward, mainly because of the high variability of shear wave velocity in complex formations. This study considered 26 shear wave profiles from downhole tests carried out in the Laga Basin (Gran Sasso, Central Apennines), where the soil can be categorised as complex owing to the chaotic succession of turbidite and Quaternary continental deposits. Downhole tests and stratigraphy were used to (i) develop a probabilistic model for predicting the shear wave profiles calibrated on the collected test data and (ii) propose an outlier detection method for estimating the first fundamental frequency of the deposit from horizontal-to-vertical spectral ratio (HVSR) analyses. Specifically, the stochastic shear wave model provides the uncertainty of the first fundamental frequency estimated from downhole tests based on a simplified mechanics-based formulation. The defined bounds, were forward uncertainty propagation following a Monte Carlo approach, have been used to define the criteria for outlier detection in HVSR frequency assessments, given an approximate estimate of the equivalent depth.

Early Result of Imaging 3D Seismic Velocity Structure In Central Java Using Double-Difference Tomography

Central Java is a part of the Sunda Arc and has relatively high seismicity due to the subduction zone between the Indo-Australian Plate and the Eurasian Plate. This study uses double-difference tomography to image the P and S wave 3D seismic velocity structures associated with tectonic patterns due to subduction zones. The data used comes from the earthquake catalogs of BMKG, BPPTKG, DOMERAPI, and MERAMEX, with a recording period from May 2004 to December 2020. The number of earthquakes that successfully relocated was 1930 from 1937 earthquakes recorded by 285 recording stations. The results of hypocentre relocation show that seismic activity in Central Java is relatively high and originates from geological structures, including subduction zones, back-thrust, and the Opak Fault. The tomogram results of the P and S wave velocity models support each other. The high seismic velocity anomaly is associated with the subduction zone of the Indo-Australian Plate to the Eurasian Plate with a maximum resolution of up to 100 km depth. Low seismic velocity anomalies are found at the Merapi-Lawu Anomaly (MLA), the Modern Volcanic Arc (MVA), the Sumbing-Sundoro-Dieng volcanic complex, the Banyumas-Cilacap sedimentary basin, and the Kendeng Basin. A low-velocity anomaly is found at a depth of about 40-50 km and a depth of 100 km, which is associated with the process of slab dehydration and partial melting. The inversion results show the impact of the Indo-Australian Plate subduction and the Eurasian Plate on volcanic activity, seismicity, and the geological structures developed in Central Java.