Wave Velocity Ratio Research Articles

Fluid upwelling across the Hikurangi subduction thrust during deep slow-slip earthquakes

Slow-slip events at global subduction zones relieve tectonic stress over days to years. Through slow-slip cycles, high fluid pressures observed at the top of subducting plates are thought to fluctuate, potentially due to the valving action of an impermeable layer near the plate interface. We model teleseismic scattering data at the Manawatu deep slow-slip patch at the Hikurangi margin in New Zealand and find high seismic P-to-S wave velocity ratios, VP/VS, in the upper ~5 km of the subducting Pacific Plate, reflecting sustained elevated fluid pressures that decrease during slow-slip and increase during inter-slow-slip periods. Within a ~ 3 km thick lower crustal layer of the overriding Australian Plate, decreasing VP/VS during inter-slow-slip periods reflects permeability reduction due to mineral precipitation. Increasing VP/VS during slow-slip reflects increasing permeability and crack density, facilitating upward fluid transfer through this layer. Our results suggest it acts as a valve to relieve high fluid pressures in the subducting slab.

Effects of a 3D basin on the near-fault ground motion by an FK-FE hybrid method

In the pursuit of accurately representing the full-process ground motion of a 3D near-fault complex site, an FK-FE hybrid method based on the idea of domain reduction is proposed. By integrating the Frequency-Wavenumber (FK) and Finite Element (FE) Methods, the hybrid method provides a new solution to seismic modeling which adaptively addresses multi-scale crustal models (from crustal to geotechnical scale) and intricate 3D site models, with consistent efficiency and precision. Then, the hybrid method is verified by comparing with results of the FK method and further validated by comparing with strong-earthquake records of the 2021 Yangbi M6.4 earthquake. Further, the proposed hybrid method is used to investigate the influence of the basin (wave velocity ratio of internal and external medium, basin's thickness) on near-fault effects due to the finite-fault source, and reveal the comprehensive mechanism of near-fault effects and basin effects. The results show that: the basin-focusing effect enhances the concentration of near-fault ground motions, and further expands the concentration range of strong-earthquake. The increases of the wave velocity ratio and basin's thickness augment the basin-focusing effect, and then the amplification effect of the basin on the fling-step effect becomes more pronounced. These results can provide a reference basis for seismic ground motion estimation and engineering seismic design in near-field complex sites.

A test on fire-induced damage of concrete with multiple parameters analysis—Based on tunnel linings of China

Fires in highway tunnels will have a significant impact on the structural performance of lining materials. A ablation test was conducted on 288 concrete specimens (1500 ×1500 ×1500 mm) with four commonly used grades of C20, C25, C30, and C35 at temperature levels of 300 ℃, 600 ℃, 750 ℃, and 900 ℃ for constant periods of 1 h, 2 h, and 4 h. The experiment revealed that: (1) From low to high temperatures, the specimens experienced cracking, spalling, explosion and eventually complete collapse; all grades of concrete remained intact or mostly intact at 600 ℃ but suffered varying degrees of damage above 750 ℃. (2) At the same fire temperature, the damage rate increased linearly with longer ablation time; while at the same ablation time, the damage rate increased quadratically with higher fire temperature. (3) The ultrasonic wave velocity ratio decreased exponentially as the ablation time increased; higher fire temperatures resulted in lower wave velocity ratios within the same ablation time period and there was a turning point at a two-hour ablation time where specimen integrity was lost. (4) For concrete specimens of the same grade and under identical exposure times to fire, as the fire temperature increased,the rate of compressive strength reduction accelerated significantly; sudden drops in compressive strength occurred at temperatures of 600 °C，750 °C，and900°C,and there was a turning point for compressive strength reduction loss after one hour's ablation to fire.(5) When subjected to high ablation temperatures,the decrease rate in concrete strength exceeded that in wave velocity,and changes in strength were more sensitive than changes in wave velocity.

Acoustic Wave Velocities in Bridge Steels and the Effects on Ultrasonic Testing

Ultrasonic testing is utilized to ensure weld quality during the fabrication of steel bridges by identifying discontinuities that are classified as either acceptable or rejectable. The classification of a discontinuity can be affected by differences in the acoustic properties of the material under test and the reference standard used for calibration. Differences in wave velocity affect the refracted angle and amplitude of refracted shear waves. As a result, indications can be missed or incorrectly classified, or incorrectly located in the material. The objective of this research study was to characterize the acoustic wave velocities in a sample of contemporary steels to better understand the range over which velocities may vary for common steels. To address this objective, a series of velocity measurements have been conducted for shear waves propagating through different directions in steel plates of different strengths and reported manufacturing processes. The study also examines the loss of signal amplitude that results from changes in the refracted angle of shear waves used for the inspection of welds. Beam splitting that may occur in anisotropic materials and the potential impact on signal amplitudes is also presented. It was shown in the research that relatively small differences in velocity between the material under test and the reference standard cause a loss of sensitivity of the test. Data presented in the paper documents wave velocity and anisotropic ratios for a population of contemporary bridge steels used for the fabrication of steel bridges and an assessment of how velocity differences affect the amplitude of reflected shear waves.

Comprehensive influence of dimensionless wave velocity and expansion ratio on energy absorption characteristics of variable wavelength traveling wave turbine

Based on the traveling wave motion of fish, this paper introduces a new type of variable wavelength traveling wave turbine that significantly differs from traditional turbine designs in its mechanical structure. By developing a two-dimensional traveling wavy plate model and conducting numerical simulations, this study investigates the relationship between the dimensionless wave velocity, variable wavelength coefficient, and expansion ratio, as well as their combined effects on the energy absorption characteristics of the variable wavelength traveling wave turbine. The results reveal that energy absorption efficiency peaks at an optimal dimensionless wave velocity, which is unaffected by changes in the variable wavelength coefficient. Furthermore, the expansion ratio significantly influences both the dimensionless wave velocity and the variable wavelength coefficient, with an optimal ratio of π∗ = 2.5 achieving 90.42 % efficiency. The energy absorption characteristics of the plate with a larger variable wavelength coefficient are found to be constrained by the expansion ratio. Additional analysis reveals that flow characteristics, such as the pressure distribution, vortex street, and velocity field surrounding the traveling wavy plate, are closely related to its energy absorption performance. These findings provide valuable insights for the design of variable wavelength traveling wave turbine.

Cardiorespiratory Fitness Benefits of High-Intensity Interval Training After Stroke: A Randomized Controlled Trial.

Limited evidence supports the effects of short-interval high-intensity interval training (HIIT) for improving cardiorespiratory fitness (V̇O2peak) after stroke. We aimed to compare the effects of 12 weeks of short-interval HIIT versus moderate-intensity continuous training (MICT) on V̇O2peak, cardiovascular risk factors, and mobility outcomes among individuals ≥6 months poststroke. This study was a multi-site, 12-week randomized controlled trial (NCT03614585) with an 8-week follow-up. Participants were randomized into 3 d/wk of HIIT (10×1 minute 80%-100% heart rate reserve interspersed with 1 minute 30% heart rate reserve [19 minutes]) or MICT (20-30 minutes 40%-60% heart rate reserve). Secondary outcomes of the trial, including V̇O2peak, cardiovascular risk factors (carotid-femoral pulse wave velocity, blood pressure, and waist-hip ratio), and mobility (6-minute walk test, 10 m gait speed), were reported. Linear mixed model analyses with a group×study time point interaction evaluated between-group differences. Of the 305 potential participants, 82 consented (mean [SD] age 64.9 [9.3] years, 32 females [39%], 1.8 [1.2] years poststroke) and were randomized to HIIT (n=42, mean [SD] baseline V̇O2peak 17.3 [5.9] mL/kg·min) or MICT (n=40, mean [SD] baseline V̇O2peak 17.2 [6.0] mL/kg·min). Participants attended 82% of visits (n=2417/2952). No adverse events occurred during the study period. A significant group×study time point interaction was found (χ2=8.46; P=0.015) for V̇O2peak at 12 weeks (mean difference, 1.81 [95% CI, 0.58-3.04]; P=0.004) whereby the HIIT group had greater gains in V̇O2peak (∆3.52 mL/kg·min [95% CI, 2.47-4.57]; P<0.001) compared with the MICT group (∆1.71 mL/kg·min [95% CI, 0.55-2.86]; P=0.001). There was no between-group difference in V̇O2peak (mean difference, 1.08 [95% CI, -0.26 to 2.42]; P=0.11) at 8-week follow-up. No group×study time point interactions were found for cardiovascular risk factors or mobility outcomes. Short-interval HIIT may be an effective alternative to MICT for improving V̇O2peak at 12 weeks postintervention. URL: https://clinicaltrials.gov; Unique identifier: NCT03614585.

Differences Between Brachial-Ankle Pulse Wave Velocity and Lower Leg Circumference Ratio in Patients With and Without Type 2 Diabetes Mellitus.

Background Vascular endothelial dysfunction in type 2 diabetes mellitus (T2DM) patients causes atherosclerosis and microvascular damage. This study investigated the relationship between leg circumference and arterial stiffness in patients with T2DM compared to non-T2DM individuals. Methods Data from two studies were combined to form T2DM (T2DM group) and non-T2DM (N group) cohorts. The variables included age, sex, systolic blood pressure (SBP), brachial-ankle pulse wave velocity (ba-PWV), ankle-brachial index, height, weight, maximum leg circumference, lower leg circumference ratio, duration of T2DM, Achilles tendon reflex disorder, and the hemoglobin A1c level. Multiple regression analysis was performed with ba-PWV as the dependent variable and the interaction term between leg circumference ratio and T2DM as the independent variable. The control variables included leg circumference ratio, T2DM, SBP, Achilles tendon reflex disorder, age, and sex. IBM SPSS Statistics for Windows, Version 23.0 (Released 2015; IBM Corp., Armonk, NY, USA) was used for the statistical analysis, with the significance level set to p < 0.05. Results The interaction term between the lower leg circumference ratio and T2DM (β = -0.17, 95% CI: -46.11 to -10.92; p < 0.01) was significantly associated with ba-PWV (AdjR² = 0.51, variance inflation factor <4.12). Simple slope analysis indicated that a decreased lower leg circumference ratio was significantly associated with an increased ba-PWV (β = -0.20, p < 0.05) in the T2DM group. No significant relationship was found in the N group (β = -0.03, p = 0.69). Conclusion A significant interaction was found between the lower leg circumference ratio and T2DM presence, indicating an association between ba-PWV and the leg circumference ratio specific to patients with T2DM. This result suggests that the leg circumference ratio can be substituted for the ba-PWV to evaluate arterial stiffness in T2DM.

Investigation on effects of water-shale interaction on acoustic characteristics of organic-rich shale in Ordos Basin, China

The water-shale interaction affect the shale structure, leading to wellbore instability and increasing drilling costs. The extent of structural changes within the shale can be determined non-destructively by analyzing its acoustic characteristics. Experiments were conducted to investigate the acoustic properties of shale from the Yanchang Formation in the Ordos Basin before and after exposure to brines of varying types, soaking times, and salinities. The study investigated the effects of brine type, soaking time, and salinity on shale’s acoustic properties, including changes in acoustic wave propagation speed, P/S wave velocity ratio, and both time-domain and frequency-domain amplitudes. The results indicate that although the type of brine has a limited impact on the water-shale interaction, KCl exhibits a significant inhibitory effect. However, the soaking time and the brine salinity have a significant impact on the acoustic properties of shale. As the soaking time increases, the decrease in wave velocity increases, the P/S wave velocity ratio increases, and the decrease in time-domain amplitude increases. The amplitude of the main frequency in the frequency domain signal also decreases with the increase of reaction time, which is consistent with the analysis results of the time domain signal. As the salinity of brine increases, the decrease in wave velocity decreases, the P/S wave velocity ratio decreases, and the decrease in time-domain amplitude decreases. The amplitude of the main frequency in the frequency domain signal also decreases with the increase of brine salinity, which is consistent with the analysis results of the time domain signal. This work establishes the relationship between water-shale interaction and acoustic characteristics, which can quantitatively evaluate the degree of interaction between water and shale without damaging shale. Furthermore, this research provides new insights and guidance for predicting drilling collapse cycles and optimizing drilling fluid compositions.

Method for Predicting Internal Defect Areas of Timber Components Based on an Adaptive Neuro-Fuzzy Inference System

ABSTRACT Internal defects in the timber components of ancient architecture can reduce their effective cross-sectional areas, deteriorate their mechanical performance, and increase the risk of structural failure. To accurately and rapidly determine the extent of internal damage in components of ancient architecture, this study performed damage detection tests on Larix gmelinii (Larch) column specimens using stress wave nondestructive testing technology. An adaptive neuro-fuzzy inference system (ANFIS) model was developed using the cross-sectional wave velocity ratio after investigating the laws of defect identification through stress-wave testing. Stress-wave detection could identify the relative positional correlation of defect areas. However, the accuracy of the defect area detection was inconsistent (8%–98%). The accuracy of the ANFIS model exhibits a diminishing trend as both parameters rejection rate and influence range increase. However, the ANFIS outperformed the stress-wave detection technique and linear regression model with correlation coefficient and prediction accuracy of 0.99 and 88%, respectively. The root mean square error for the ANFIS was reduced by 79% and 70% compared to the stress wave detection method and linear regression model, respectively. Thus, the ANFIS model can precisely forecast areas of internal damage in timber components of historical edifices and can be used to evaluate the safety of ancient timber buildings.

Exploration of shock–droplet interaction based on high-fidelity simulation and improved theoretical model

Shock–droplet interaction in the early stage involves intricate wave structures. Investigating this phenomenon is inherently challenging due to the fine spatial and temporal scales involved. Past research has suggested that the occurrence of cavitation, marked by a negative peak pressure, is linked to the focus of the reflected expansion wave. In this study, a high-fidelity compressible numerical approach is utilized to replicate the initial phase of shock–droplet interactions. The location of the negative peak pressure is meticulously documented and compared with experimental measurement and numerical results. Results indicate a strong alignment between the negative peak pressure positions identified through numerical simulations and the focal points identified in theoretical models for low gas–liquid wave velocity ratios. However, this alignment is notably disrupted when dealing with higher gas–liquid wave velocity ratios. Further enhancements are made to the theoretical model, enabling a more precise depiction of internal wave structures and focus points, particularly under conditions of high gas–liquid wave velocity ratios. The study delves into the various factors influencing internal pressure fluctuations within the liquid droplet, categorizing them into four phases: the shock wave effect, relaxation effect, fluctuation effect, and expansion wave effect. Analysing the pressure decrease portion reveals that while the converging of the reflected expansion wave leads to a substantial pressure drop, it accounts for only a fraction of the total pressure variation. Consequently, any model predicting negative peak pressure positions must comprehensively consider all contributing factors.

Aging related changes in cardiovascular system in healthy female population: photoplethysmography method and DFA analysis

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Science Technological Development and Innovation Background The cardiovascular system undergoes dynamic changes during the biological aging in humans, leading to chronic cardiovascular and cerebrovascular diseases. Purpose Developing the novel method for non-invasive monitoring of age induced changes in arterial vessels. Methodology The pilot study was performed on 58 women, in good health, non-smokers, between the ages of 20 and 70, divided into three age groups. All subjects underwent arterial blood pressure measurement using a photoplethysmography sensor. Recordings were performed in left carotid artery and the left index finger area. Arterial blood flow waveform was then analyzed using DFA analysis, calculating the values of the scalar coefficients α1 and α2. Based on the waveform time interval shift between the standing and supine positions, the pulse wave velocity (PWV) ratio was determined. Results Systolic and diastolic arterial pressure showed a slight linear increase with the age, but without significant difference between the three age categories (p &amp;gt; 0.5). Also, the PWV ratio between the supine and standing positions did not show a statistically significant increase between the age groups. Only scalar coefficients ratio α1/α2 demonstrated a significant difference in value between all age categories. Conclusion In subjects included in this pilot study, only the scalar coefficients ratio varied significantly with the age, indicating the occurrence of structural changes in the cardiovascular system caused by biological aging.

Analysis of subsidence zone of the village access road in Jatirunggo, Semarang Regency using microtremor data

The rehabilitation of the subsidence phenomenon in Jatikurung sub-village, Jatirunggo village, Pringapus Subdistrict, Semarang Regency, Central Java, has been carried out for a long time however, it has never been successful. Every time an embankment is made, it is only a matter of time before another subsidence occurs. This research aims to investigate the subsurface structure of the subsidence sites. It is proposed to be used as a reference for structural planning in the treatment of road subsidence. Subsurface information is very useful in addressing the subsidence problem more effectively and precisely. The method used was by recording microtremor data and analyzing shear wave velocity and Poisson ratio as parameters to determine the type of subsurface layer. The obtained results are in the form of clay layers to bedrock layers at a depth of 35m. The movement occurred because of the soft or loose soil below and at the edge of the road above the impermeable clay layer. In addition, to the north side of the collapse point is a fairly deep cliff, which is a burden on the bedrock. When it was raining, the soil filled with water and there was even a flow of water in the soil deposits (piping) resulting in the ground movement toward the lower part.

RESEARCH, DEVELOPMENT AND IMPLEMENTATION OF METHODS AND TECHNOLOGIES OF ACOUSTIC STRAIN GAUGING OF SPLIT JOINTS OF LIQUID ROCKET ENGINES FOR SPACE LAUNCH VEHICLES

A review of the results of research, development and implementation of methods and technologies of acoustic strain measurement of split joints of liquid rocket engines for space launch vehicles is presented. A brief description of methods for measuring the incremental time of propagation of ultrasonic longitudinal waves and the ratio of longitudinal and shear wave velocities is given. The description of the developed and enacted GOST R 52889‒2007 “Non-destructive testing. Acoustic method of control of tightening force of threaded joints. General requirements”. Acoustic strain gauges, including those in regular operation at NPO Energomash, are described. A brief description of the specialized program “Acoustic Tensometer” is given, as well as a set of standard samples for performance control and preliminary adjustment of devices and calibration bench. The method of acoustic tensometry based on the ratio of longitudinal and shear wave velocities proposed by the specialists of NPO “Energomash” is described. The application of the method of acoustic strain gauge tightening of detachable joints, along with the improvement of the LPRD production technology, made it possible to completely eliminate leakage and leakage failure.

Stability analysis of circular tunnels using spatiotemporal accelerations formulated considering heterogeneity of seismic wave propagation velocities

The space–time dependent horizontal and vertical seismic accelerations in a soil medium owing to the inhomogeneity in the shear and primary wave propagation velocities were analytically derived satisfying the boundary conditions on the ground surface and the base. The developed analytical formulations were applied to study the influence of wave velocity heterogeneity on the support pressure required for the circular tunnel stability placed in granular soils using the stress-based limit analysis in conjunction with finite elements. The support pressure was determined as the maximum normal stress exerted by the surrounding earth at its ultimate failure on the tunnel boundary. Further, the effect of frequency of seismic waves on the seismic accelerations, magnitude of tunnel support pressure and the variation of normal stress around the tunnel periphery has been presented in detail. The support pressure was found to be higher considering the heterogeneous wave velocity than the uniform one. A lower dimensionless frequency resulted in higher support pressures for a lower wave velocity ratio and higher power parameter of the power law used to model the wave velocity profile. Otherwise, for higher wave velocity ratio, the effect of power parameter diminishes, and the support pressure is higher for higher dimensionless frequency.

Longitudinal seismic analysis for underground structures passing through soft-hard strata based on periodic stratum deformation

Poor geological conditions, e.g., soft and hard strata, have a significant impact on the seismic response of underground structures. In this study, a series of longitudinal seismic analysis for underground structures passing through soft-hard strata were conducted based on the concept of periodic stratum deformation. Firstly, the analytical expressions of stratum deformation in soft-hard strata at the oblique incidence of plan P-, and S- wave were obtained via decomposing the stratum deformation into the reflected- and transmitted wave fields. Then, the wave propagation history in soft-hard strata in the time domain was transformed into strata deformation in a period via introducing concept of the periodic stratum deformation. Base on the proposed expressions, a self-developed Python program was implemented into finite element software ABAQUS to establish seismic analysis model and to calculate the longitudinal seismic response of underground structures. Finally, example analyses were conducted to study the influence of plane P- and S- wave, wave velocity ratio of soft and hard media, as well as incident wave angle on the seismic response of underground structures located in soft- hard strata. This study may provide a reference for seismic design of underground structures located in soft- hard strata.

Theoretical modeling and dynamic analysis of designable grillages for repairing material surface defect

Designing structural grillages is an innovative solution to repair material surface defects. The grillages have advantages as lightweight and directionally enhanced, but their stability and stress concentration under dynamic loads may pose significant risks. Three analytical models of grillages above a semicircular defect are constructed. The analytical solution of the frequency-domain wave field around the semicircular defect under SH wave incidence is solved. The complex variable function method is introduced to simplify the wave field expression. The accuracy is verified by comparing it with classic examples. Applying the Modified Time-Frequency Transform to obtain the time-domain wave field. Based on the Multipoint Transient Input Method (MTIM), the transient surface displacement response of the grillage above the defect is derived, mainly discussing the superposition behavior of input waves in the grillage. MTIM is based on the analytical solution of local time-domain wave field and takes the time histories of the surface characteristic points as the wave input. It has been validated as an effective method for studying the dynamic response of structures. The numerical results show that grillage form, incident angle, and wave velocity ratio are important factors affecting the structural responses of grillage above the defect. This research aims to reveal the propagation characteristics of waves in grillages in filling material defects, providing theoretical guidance for the design and application of grillages in this field.

Study of 3-D velocity structure characteristics in Dadu river Houziyan reservoir area at different impoundment stages

High-resolution three-dimensional VP, VS and VP/VS images in the Houziyan Reservoir Area were obtained by using Fast Marching Tomography Package (FMTOMO) with the travel time data from 6330 seismic events monitored by the Houziyan Reservoir Seismic Network. This analysis yielded the 3-D velocity structure, including longitudinal wave velocity (VP), shear wave velocity (VS), and the ratio of longitudinal and shear wave velocity (VP/VS) at different impoundment stages. The data changes at various impoundment times, depths of sections, and directions of profiles were analyzed to obtain these results. The final findings demonstrate the following results: 1) Through tomographic analysis, it was determined that the underground velocity structure in the Houziyan reservoir area was anisotropic before impoundment. 2) The area of high wave velocity increases in stage 1, stage 3, and stage 4. The area of low wave velocity increases in stage 2, especially in depth, indicating significant changes in the underground velocity structure at different impoundment stages. 3) Compared to the changes in underground velocity structures in other reservoirs after impoundment, the Houziyan reservoir exhibited a unique pattern. 4) In general, the underground velocity structure displayed an overall increasing trend after impoundment. However, it also exhibited instances of decreasing velocity, reflecting continuous dynamic adjustments to the underground velocity structure after impoundment. These conclusions highlight the impact of impoundment in the reservoir area on the underground velocity structure and provide scientific theoretical support for seismic risk assessment following impoundment in the reservoir area.

Investigation on the dynamic characteristics of anchor rods considering size effect and pull-out loads based on IIR-FDM

When the surrounding rock of tunnel anchor bars has boundaries, the signals obtained from non-destructive testing (NDT) of anchor rods will be simultaneously affected by size effects and pull-out loads, leading to potential misinterpretation of the test results. In order to accurately assess the anchorage quality of anchor rods under this interference, NDT and numerical simulations of anchor rods subjected to different anchorage quality were conducted under the influence of size effects and pull-out loads. A signal filtering method, which combines the infinite impulse response-finite difference method, was proposed for identify the impact of size effects. The study analyzed the variations in wave velocity and fundamental frequency of anchor rods with anchorage defects and intact anchor rods under the influence of size effects and pull-out loads. The results indicate that the IIR-FDM method, in comparison to the traditional wavelet method, provides better agreement between the calculated wave velocities and existing findings. With the increase of size effect, the wave velocity and amplitude ratio of the anchor rods decrease, and the fundamental frequency increases first and then decreases. As the working load on the anchor rods increases, the wave velocity initially decreases, then rises, while the fundamental frequency initially increases and then experiences a slight decrease. The presence of anchorage defect results in an increase in the wave velocity and amplitude ratio of the anchor rods, while causing a decrease in the fundamental frequency. This effect of defects on wave velocity and fundamental frequency is more pronounced at lower loads. The wave velocity after IIR-FDM processing has a small error with the simulated wave velocity, indicating the reliability of the processing method.

Blind magmatism abets nonvolcanic continental rifting

Tectonic forces alone cannot drive rifting in old and thick continental lithosphere. Geodynamic models suggest that thermal weakening is critical for lithospheric extension, yet many active rifts lack volcanism, seeming to preclude this process. We focus on one such rift, the Tanganyika-Rukwa segment of the East African Rift System, where we analyze local seismicity for shear wave anisotropy and couple the results with numerical modeling. The strongest splitting measurements are from earthquakes with paths sampling lower crustal regions of high compressional-to-shear wave velocity ratios and have fast polarization directions parallel to the local mantle flow, implying the existence of oriented melt lenses. This lower crustal magmatism and observed high surface heat flow are consistent with substantial lithospheric weakening and explain the enigmatic relief and increasing strain accommodation along the rift axis. We conclude that progressive nonvolcanic rifting is assisted by deep crustal melts yet to breach the surface.

Site classification Based on Shear Wave Velocity Inversion in The Jlantah Dam Construction Project using the HVSR (Horizontal to Vertical Spectral Ratio) Analysis Method

This research was conducted with the aim to test whether the results of the inversion of the HVSR curve can be used as complementary data for N-SPT values in classifying areas according to site classification. The inversion result in the form of shear wave velocity (VS ) is then compared directly with the N-SPT data in several boreholes. Ellipticity curve method is used for inversion. The data generated in this study are dominant frequency, Amplitude Peak, and H/V curve as a result of the HVSR analysis performed on microtremor data. Furthermore, an inversion was carried out on the H/V curve by taking into account secondary data in the form of borehole, shear wave velocity, density and poisson ratio for each type of lithology. The dominant frequency value obtained has a value range of 0.33 to 17.15 Hz. The Amplitude Peak obtained in the study area has a value range of 1.81 – 11.4. The inversion (VS ) value has a range of 110.5 m/s – 400 m/s, so it is included in the classification of Soft Soil, Medium Soil, and Hard Soil and Soft Rock. The correlation of and N-SPT show that inversion method with HVSR analysis of microtremor data is quite reliable as supporting data for N-SPT. Considering cons of drilling, the method used in this study can be a new alternative for use in construction projects because it can be carried out at a relatively low cost, and is quite simple in terms of data acquisition and processing.