Velocity VS Research Articles

Deep neural network–powered ground-motion models for acceleration spectrum intensity, Housner’s spectrum intensity, and displacement spectrum intensity

This study develops new ground-motion models (GMMs) for acceleration spectrum intensity ( ASI), Housner’s spectrum intensity ( SI), and displacement spectrum intensity ( DSI) using the NGA-West2 database. A deep neural network (DNN)-based mixed-effects regression approach is presented for the model development accounting for the between-event and within-event variability. The performance evaluation results show the generally unbiased and reliable predictions with R-squared values exceeding 0.9 on both training and testing data. A hybrid-scenario method is subsequently employed to conduct the semi-blind test on large datasets that are not directly used in model development, illustrating favorable model generalization capability. Meanwhile, the DNN models exhibit physically reasonable magnitude and distance scaling characteristics, producing comparable median trends with the existing NGA-West2 GMM-embedded indirect approach. Yet, the major advantage of the new models is their ability to achieve lower statistical dispersion using fewer input parameters (i.e. (moment magnitude Mw, rupture distance Rrup, upper 30-m shear-wave velocity VS30, and focal mechanism indicator) or ( Mw, Rrup, VS30, focal mechanism indicator, depth to top of rupture Ztor, and depth to 1 km/s shear-wave velocity, Z1)). Incorporating Ztor and Z1 into the DNN models yields 10%–20% reduction in mean squared error, while the benefit of adding predictor variables is less pronounced for the functional form-based classical regression models. The new models are applicable to shallow crustal earthquakes with 3 ≤ Mw ≤ 7.9, 0 ≤ Rrup ≤ 400 km, and 150 ≤ VS30 ≤ 1500 m/s.

Study on the influence of collision conditions on the surface morphology of compound droplets

In this study, a three-dimensional compound droplet collision numerical model is established by using volume of fluid. The morphological evolution of compound hollow droplets affected by high-speed solid droplet was studied in detail. Parameterized analysis is conducted on the velocity VS, center distance ϕ, and diameter ζ of high-speed small droplets. Through the analysis of the compound droplets flow field, it is found that the broken mode of compound droplets is caused by the increase in Pn (dimensionless pressure) and θ (velocity angle). The results show that the surface Pn of compound droplets is positively correlated with the velocity VS of high-speed small droplets, while there is a more complex relationship with the dimensionless center distance ϕ and dimensionless diameter ζ. When the values of ϕ and ζ are appropriate, Pn can reach its maximum value. The broken mode of compound droplets can be divided into three categories: shear deformation, shear crushing, and violent crushing.

Novel techniques for in situ estimation of shear-wave velocity and damping ratio through MASW testing part II: a Monte Carlo algorithm for the joint inversion of phase velocity and phase attenuation

SUMMARY This paper deals with in situ characterization of the small-strain shear-wave velocity VS and damping ratio DS from an advanced interpretation of Multi-channel Analysis of Surface Waves (MASW) surveys. A new approach based on extracting Rayleigh wave data using the CFDBFa method has been discussed in the companion paper. This paper focuses on mapping the experimental Rayleigh wave phase velocity and attenuation into profiles of VS and DS versus depth, which is achieved through a joint inversion procedure. The joint inversion of phase velocity and attenuation data utilizes a newly developed Monte Carlo global search algorithm, which implements a smart sampling procedure. This scheme exploits the scaling properties of the solution of the Rayleigh eigenvalue problem to modify the trial earth models and improve the matching with the experimental data. Thus, a reliable result can be achieved with a limited number of trial ground models. The proposed algorithm is applied to the inversion of synthetic data and of experimental data collected at the Garner Valley Downhole Array site, as described in the companion paper. In general, inverted soil models exhibit well-defined VS profiles, whereas DS profiles are affected by larger uncertainties. Greater uncertainty in the inverted DS profiles is a direct result of higher variability in the experimental attenuation data, the limited wavelength range at which reliable values of attenuation parameters can be retrieved, and the sensitivity of attenuation data to both DS and VS. Nonetheless, the resulting inverted earth models agree well with alternative in situ estimates and geological data. The results stress the feasibility of retrieving both stiffness and attenuation parameters from active-source MASW testing and the effectiveness of extracting in situ damping ratio estimates from surface wave data.

Novel techniques for in situ estimation of shear-wave velocity and damping ratio through MASW testing – I: a beamforming procedure for extracting Rayleigh-wave phase velocity and phase attenuation

SUMMARY A robust, in situ estimate of shear-wave velocity VS and the small-strain damping ratio DS (or equivalently, the quality factor QS) is crucial for the design of buildings and geotechnical systems subjected to vibrations or earthquake ground shaking. A promising technique for simultaneously obtaining both VS and DS relies on the Multichannel Analysis of Surface Waves (MASW) method. MASW can be used to extract the Rayleigh wave phase velocity and phase attenuation data from active-source seismic traces recorded along linear arrays. Then, these data can be inverted to obtain VS and DS profiles. This paper introduces two novel methodologies for extracting the phase velocity and attenuation data. These new approaches are based on an extension of the beamforming technique which can be combined with a modal filter to isolate different Rayleigh propagation modes. Thus, the techniques return reliable phase velocity and attenuation estimates even in the presence of a multimode wavefield, which is typical of complex stratigraphic conditions. The reliability and effectiveness of the proposed approaches are assessed on a suite of synthetic wavefields and on experimental data collected at the Garner Valley Downhole Array and Mirandola sites. The results reveal that, under proper modelling of wavefield conditions, accurate estimates of Rayleigh wave phase velocity and attenuation can be extracted from active-source MASW wavefields over a broad frequency range. Eventually, the estimation of soil mechanical parameters also requires a robust inversion procedure to map the experimental Rayleigh wave parameters into soil models describing VS and DS with depth. The simultaneous inversion of phase velocity and attenuation data is discussed in detail in the companion paper.

Hard-Rock κ0 at KiK-Net Sites in Japan

ABSTRACT Site-specific seismic hazard studies require the knowledge of the shear-wave velocity VS and the high-frequency site attenuation parameter κ0 at the reference rock level at depth. The latter one (called κ0,ref) is often not available and hard to derive. In this study, we make use of the KiK-net database in Japan that consists of surface and colocated downhole sensors. We select 175 sites where the bottom sensor is deployed at rock or hard-rock conditions resulting in a database with many recordings at VS≥1500 m/s. This allows us to tackle two questions: first, is it possible to derive κ0,ref from surface recordings? Second, does κ0 reach an asymptotic level at high VS that could be used as a κ0,ref in site-specific seismic hazard studies? Our results show that measures of κ0 derived from S and coda waves are equivalent. Thus, it is not possible to obtain κ0,ref from surface recordings using coda waves. On the other hand, S-wave measurements of κ0 from surface rock sites are close to κ0,ref if VS≥760 m/s or if the sedimentary cover is thin. The values of κ0 decrease with increasing VS and reach an asymptotic value. The scatter in the so obtained κ0,ref is high, but it can be reduced by selecting subregions with similar geological conditions. Finally, we observe that borehole and surface κ0 are correlated, and that the variability of κ0,ref is only slightly reduced compared to κ0 at the surface. Although we cannot exclude any influence of source effects, our findings indicate that κ0,ref has to be considered as a deep site parameter.

Shallow S wave velocity profile from active source seismic data at the Apollo 14 landing site based on virtual multichannel analysis of surface waves

We used active source seismic data at the Apollo 14 landing site to investigate the shallow S wave velocity structure (from the surface to a depth of 10 m) of the Moon. We applied seismic interferometry to data from shots located between two geophones to construct a virtual shot gather for multichannel analysis of surface waves (MASW). We included continuous wavelet transform processing in the MASW analysis to improve the signal-to-noise ratio of the data before estimating the S wave velocity VS profile. The resultant profile showed gradual increase in S wave velocity from the surface (VS = ∼50 m/s) to a depth of 6 m (VS = ∼100 m/s), followed by a harder layer with S wave velocity of 110 m/s. This study demonstrated that future extraterrestrial active seismic surveys can be accomplished faster, with simpler field geometry, and using fewer shots and receivers than past missions, thus reducing the payload and cost of future exploration missions.

Sound velocities of natural clinohumite at high pressures and implications for seismic velocities of subducted slabs in the upper mantle

Clinohumite is one of the major transformation products of serpentine at high pressures and an important H2O and F carrier in the upper mantle at subduction zones. Sound velocity measurements on clinohumite under high P-T conditions are crucial for modeling slab structure, arc magmatism, seismicity, and deep H2O cycling process. The compressional (P-) and shear (S-) wave velocities of a natural F-bearing clinohumite [Mg8.17Ti0.19Fe0.01(SiO4)4O0.38(OH)1.17,F0.74] were investigated using ultrasonic interferometry technique up to 14.6 GPa at room temperature in a multi-anvil apparatus. The variations of both the P- and S-wave velocities of clinohumite with pressure are the smallest when compared to the common anhydrous and other dense hydrous magnesium silicate (DHMS) phases in the upper mantle. Finite strain analysis of the acoustic velocities and density data yields the adiabatic bulk (KS) and shear (G) moduli and their pressure derivatives: KS0 = 121.0(5), G0 = 76.5(2), KS’ = 3.9(1), G' = 1.1(1). Furthermore, the density and seismic velocity profiles of subducted harzburgite assemblages with various degrees of hydration were calculated up to 14 GPa along an isotherm at 1073 K. Our results indicate that clinohumite has a larger effect on the density of peridotite than phase A and 23 Å phase under the same degree of hydration of peridotite in the upper mantle. Moreover, the VP and VS velocity contrasts between dry harzburgite and harzburgite with 2 wt% H2O from clinohumite are about ∼1.6% and ∼ 1.0%.

The Urban Underground Space beneath the Karst Basin of Guilin, China, Revealed by Ambient Seismic Noise Tomography

Abstract Detection of hidden faults and sedimentary layers in the urban subsoil is significant for the utilization of the underground space, earthquake hazard mitigation, and so forth. Guilin, located in southwest China, is well known for the development of the most typical karst landform in the world and has become an international tourist city that needs scientific planning and knowledge of the urban underground space. After collecting waveform data recorded continuously over a period of about 1.5 months by a dense array of 114 short-period seismic stations installed in and around Guilin, we adopt ambient seismic noise cross-correlation method to extract Rayleigh-wave phase velocity dispersion curves within the period range from 0.5 to 5 s and to obtain a high-resolution S-wave velocity (VS) model of the shallow crust above 9 km using surface-wave tomography. The vertical VS gradient image indicates that the sediment thickness of the Guilin Karst basin is about 1–3 km. Sedimentary layers are relatively thick between Yanshan Mountain and Haiyang Mountain, and along the Yi river valley, where karst groundwater may be abundant and used as an important option for urban water supply. Both the absolute VS velocity image and the relative VS anomaly image clearly reveal the occurrence, location, and deep extension characteristics of major faults. Longsheng–Yongfu, Nanning–Guilin, Yaoshan–Yanshan, Baishi, and Guanyang–Hengyang may be regional deep faults cutting through the upper crust at least. The evolution of the basin is mainly controlled by the steep dipping Longsheng–Yongfu and Baishi faults, and partially controlled by the gently dipping Nanning–Guilin fault in the interior of the basin. The Nanning–Guilin fault is an active and partially buried fault obliquely crossing Guilin city. Urban seismic imaging, such as the new VS tomography presented here, can play an important role in understanding tectonic and tectonic-subsidence earthquake hazards associated with these buried faults.

Predicting shear wave velocity from conventional well logs with deep and hybrid machine learning algorithms

Shear wave velocity (VS) data from sedimentary rock sequences is a prerequisite for implementing most mathematical models of petroleum engineering geomechanics. Extracting such data by analyzing finite reservoir rock cores is very costly and limited. The high cost of sonic dipole advanced wellbore logging service and its implementation in a few wells of a field has placed many limitations on geomechanical modeling. On the other hand, shear wave velocity VS tends to be nonlinearly related to many of its influencing variables, making empirical correlations unreliable for its prediction. Hybrid machine learning (HML) algorithms are well suited to improving predictions of such variables. Recent advances in deep learning (DL) algorithms suggest that they too should be useful for predicting VS for large gas and oil field datasets but this has yet to be verified. In this study, 6622 data records from two wells in the giant Iranian Marun oil field (MN#163 and MN#225) are used to train HML and DL algorithms. 2072 independent data records from another well (MN#179) are used to verify the VS prediction performance based on eight well-log-derived influencing variables. Input variables are standard full-set recorded parameters in conventional oil and gas well logging data available in most older wells. DL predicts VS for the supervised validation subset with a root mean squared error (RMSE) of 0.055 km/s and coefficient of determination (R2) of 0.9729. It achieves similar prediction accuracy when applied to an unseen dataset. By comparing the VS prediction performance results, it is apparent that the DL convolutional neural network model slightly outperforms the HML algorithms tested. Both DL and HLM models substantially outperform five commonly used empirical relationships for calculating VS from Vp relationships when applied to the Marun Field dataset. Concerns regarding the model's integrity and reproducibility were also addressed by evaluating it on data from another well in the field. The findings of this study can lead to the development of knowledge of production patterns and sustainability of oil reservoirs and the prevention of enormous damage related to geomechanics through a better understanding of wellbore instability and casing collapse problems.Graphical abstract

0–5 Hz deterministic 3-D ground motion simulations for the 2014 La Habra, California, Earthquake

SUMMARYWe have simulated 0–5 Hz deterministic wave propagation for a suite of 17 models of the 2014 Mw 5.1 La Habra, CA, earthquake with the Southern California Earthquake Center Community Velocity Model Version S4.26-M01 using a finite-fault source. Strong motion data at 259 sites within a 148 km × 140 km area are used to validate our simulations. Our simulations quantify the effects of statistical distributions of small-scale crustal heterogeneities (SSHs), frequency-dependent attenuation Q(f), surface topography and near-surface low-velocity material (via a 1-D approximation) on the resulting ground motion synthetics. The shear wave quality factor QS(f) is parametrized as QS, 0 and QS, 0fγ for frequencies less than and higher than 1 Hz, respectively. We find the most favourable fit to data for models using ratios of QS, 0 to shear wave velocity VS of 0.075–1.0 and γ values less than 0.6, with the best-fitting amplitude drop-off for the higher frequencies obtained for γ values of 0.2–0.4. Models including topography and a realistic near-surface weathering layer tend to increase peak velocities at mountain peaks and ridges, with a corresponding decrease behind the peaks and ridges in the direction of wave propagation. We find a clear negative correlation between the effects on peak ground velocity amplification and duration lengthening, suggesting that topography redistributes seismic energy from the large-amplitude first arrivals to the adjacent coda waves. A weathering layer with realistic near-surface low velocities is found to enhance the amplification at mountain peaks and ridges, and may partly explain the underprediction of the effects of topography on ground motions found in models. Our models including topography tend to improve the fit to data, as compared to models with a flat free surface, while our distributions of SSHs with constraints from borehole data fail to significantly improve the fit. Accuracy of the velocity model, particularly the near-surface low velocities, as well as the source description, controls the resolution with which the anelastic attenuation can be determined. Our results demonstrate that it is feasible to use fully deterministic physics-based simulations to estimate ground motions for seismic hazard analysis up to 5 Hz. Here, the effects of, and trade-offs with, near-surface low-velocity material, topography, SSHs and Q(f) become increasingly important as frequencies increase towards 5 Hz, and should be included in the calculations. Future improvement in community velocity models, wider access to computational resources, more efficient numerical codes and guidance from this study are bound to further constrain the ground motion models, leading to more accurate seismic hazard analysis.

Anomalous elastic behavior of tantalum at high pressures: Experimental and theoretical studies

Elastic wave velocities of polycrystalline tantalum have been measured up to 13.6 GPa at room temperature using ultrasonic interferometry technique in a multi-anvil apparatus. The bulk and shear moduli, as well as their pressure derivatives are obtained using Eulerian 3rd order finite strain equations, yielding KS0 = 193.9(29) GPa, G0 = 69.3(10) GPa, KS0′ = 3.18(5) and G0′ = 0.88(1). The Steinberg-Guinan yield stress model is examined using the current shear modulus and its pressure derivative, where a slightly lower A0 = 0.0127 GPa−1 compared to previous studies is obtained. First-principles calculations on the elasticity of tantalum have also been performed up to 200 GPa. Anomalous softening of the elastic shear constant C44 and shear wave velocity VS is observed between 80– 180 GPa, whereas the anisotropy shows a softening-stiffening behavior with increasing pressure and reaches a minimum at around 150 GPa. Such anomalies might commonly originate from the nesting of Fermi surface for Group VB metals.

Stiffness and strength development of the soft clay stabilized by the one-part geopolymer under one-dimensional compressive loading

In this paper, the one-part alkali-activated geopolymer was adopted as the soil binder to stabilize the soft clay under the one-dimensional compressive loading. Factors influencing the stiffness and strength of the one-part geopolymer stabilized soil such as the proportion of silicon-aluminum raw materials, the mass ratio of solid NaOH (NH) to raw materials and the water-binder ratio were taken into account. The stiffness development of the one-part geopolymer stabilized soft clay under one-dimensional compressive loading was investigated by an improved transducer system equipped with a pair of bender extender elements and the tactile pressure sensor, from which the time history of earth pressure coefficient (i.e., K0) and elastic wave velocity (i.e., the compression wave velocity VP and the shear wave velocity VS) of the stabilized soil sample could be measured, respectively. Furthermore, the unconfined compressive strength (UCS) of the stabilized soil sample cured under varied one-dimensional compressive loadings was tested to reveal the strength development of the geopolymer stabilized soil sample. Among different mixing proportions, the alkali-activated binary precursor [90% ground granulated blast furnace slag (GGBFS) and 10% fly ash (FA)] exhibits the highest performance in terms of the VS, VP and UCS of the geopolymer stabilized soil sample when the activator/precursor and water/solid ratio are 0.15 and 0.7 (i.e., the 4.67 mol/L of NH solution), respectively. The prediction of UCS for the one-part geopolymer stabilized soft clay was proposed and established based on the elastic wave velocity (i.e., VS and VP). The outcome of the current study sheds light on the practical use of the one-part alkali-activated geopolymer as a soil binder in ground improvement.

Implications of high-frequency decay parameter, “κ-kappa”, in the estimation of kinematic soil-structure interaction effects

In the present study, the difference between the peak seismic response measures recorded on building basements and those at nearby free-field conditions is studied by means of estimating the high-frequency spectral decay parameter, “κ” (known as “kappa”). Computation of “κ” is performed for selected accelerographic stations belonging to three strong motion networks, namely the Hellenic National Accelerographic Network (HNAN) in Greece, the Center for Engineering Strong Motion Data (CESMD) in California, USA and the Building Research Institute (BRI) in Japan. Parameter “κ” is computer according to Anderson and Hough (1984), while an automated signal energy-based procedure is developed to calculate the S-wave windows of each waveform, accounting for any errors. Site-specific restrictions on the upper frequency limit, f2, for the calculation of “κ” at the foundation level are imposed, based on the empirical transfer functions between foundation and free-field motions. Based on the above procedure, non-linear regression analyses are conducted to relate “κ”, as computed for free-field and foundation motions (κff, - κfnd), to magnitude Mw, source-to-site distance Repi and shear wave velocity VS30. Simulation of ground motions though the point-source stochastic method is accomplished, utilizing the regression expression to define “κ” and assess its effectiveness to predict the variation of intensity between free-field and foundation motions as a proxy for assessing soil-structure interaction effects. It is shown that the regression-based expressions, combined with stochastic simulations, consist a promising tool for correcting seismic motions recorded at a building foundation or basement levels and thus, for reliably predicting the corresponding intensity and characteristics of the actual “building-free” ground motions.

Self-generated ultraviolet radiation in molecular shock waves

Context. Shocks are ubiquitous in the interstellar and intergalactic media, where their chemical and radiative signatures reveal the physical conditions in which they arise. Detailed astrochemical models of shocks at all velocities are necessary to understand the physics of many environments including protostellar outflows, supernova remnants, and galactic outflows. Aims. We present an accurate treatment of the self-generated ultraviolet (UV) radiation in models of intermediate velocity (VS = 25–60 km s−1), stationary, weakly magnetised, J-type, molecular shocks. We show how these UV photons modify the structure and chemical properties of shocks and quantify how the initial mechanical energy is reprocessed into line emission. Methods. We develop an iterative scheme to calculate the self-consistent UV radiation field produced by molecular shocks. The shock solutions computed with the Paris–Durham shock code are post-processed using a multi-level accelerated Λ-iteration radiative transfer algorithm to compute Lyman α, Lyman β, and two-photon continuum emission. The subsequent impacts of these photons on the ionisation and dissociation of key atomic and molecular species as well as on the heating by the photoelectric effect are calculated by taking the wavelength dependent interaction cross-sections and the fluid velocity profile into account. This leads to an accurate description of the propagation of photons and the thermochemical properties of the gas in both the postshock region and in the material ahead of the shock called the radiative precursor. With this new treatment, we analyse a grid of shock models with velocities in the range VS = 25–60 km s−1, propagating in dense (nH ≥ 104 cm−3) and shielded gas. Results. Self-absorption traps Lyα photons in a small region in the shock, though a large fraction of this emission escapes by scattering into the line wings. We find a critical velocity VS ~ 30 km s−1 above which shocks generate Lyα emission with a photon flux exceeding the flux of the standard interstellar radiation field. The escaping photons generate a warm slab of gas (T ~ 100 K) ahead of the shock front as well as pre-ionising C and S. Intermediate velocity molecular shocks are traced by bright emission of many atomic fine structure (e.g. O and S) and metastable (e.g. O and C) lines, substantive molecular emission (e.g. H2, OH, and CO), enhanced column densities of several species including CH+ and HCO+, as well as a severe destruction of H2O. As much as 13–21% of the initial kinetic energy of the shock escapes in Lyα and Lyβ photons if the dust opacity in the radiative precursor allows it. Conclusions. A rich molecular emission is produced by interstellar shocks regardless of the input mechanical energy. Atomic and molecular lines reprocess the quasi totality of the kinetic energy, allowing for the connection of observable emission to the driving source for that emission.

Rigorous test of the performance of shear-wave velocity correlations derived from CPT soundings: A case study for Groningen, the Netherlands

An improved correlation between shear-wave velocity VS and cone penetration test (CPT) parameters was derived for the Groningen region, the Netherlands, using a set of 154 pairs of CPTs and seismic CPTs. An analysis of a high-quality subset showed that the subdivision into Holocene versus Pleistocene intervals or into cohesive versus non-cohesive intervals did not significantly improve correlation, nor did filtering out of the transition intervals between clay and sand in the non-cohesive dataset. In addition, using qt or qc resulted in similar regression results. We therefore propose a single new equation and we applied this to all available CPTs in the region. The analysis of the fitting bias showed that there is a trend relative to the measured VS. We therefore recommend performing SCPT measurements when very soft soils (VS < ~100 m/s) are encountered, rather than relying on the empirical correlation based on CPT parameters.The comparison of the VS30 values from CPTs to the model VS30 of Groningen shows that correlation is excellent: 90% of the calculated VS30 values from the CPTs fall within one standard deviation of the VS30 of the corresponding geological zone of the model. Although the resulting CPT-VS correlation is specific for the Groningen region, the approach can be applied to other regions with a paired SCPT-CPT dataset.

An empirical relationship between resonance frequency, bedrock depth and VS30 for Croatia based on HVSR forward modelling

Seismic bedrock depth represents one of the crucial steps in site response analysis as the input seismic ground motion is propagated from the bedrock level through soil profile column to estimate surface ground motion. In the last two decades, several studies estimated bedrock depth using microtremor horizontal-to-vertical-spectral ratio fundamental (resonance) frequency and known (mostly boreholes) bedrock depth in different regions through power-law regression. In this study, seismic bedrock (H800—depth of the bedrock formation identified by shear wave velocity VS ≥ 800 m/s) is estimated using H/V forward modelling routine in which shear wave velocity profile from geophysical measurements was used as an initial soil model. Based on geological, geophysical and microtremor data, empirical relationships between average shear wave velocity in top 30 m, resonance frequency and bedrock depth are derived. Given evaluation of sedimentary thicknesses showed to be within the range of published studies for similar geological and site characteristics if the errors between different methods, approaches and site parameters are considered. The main limitation to validate proposed relationships is the lack of realistic deep borehole data like in similar studies. Further work is required that should include deep data from borehole drilling, seismic refraction and reflection or vertical electrical sounding. The intention is that presented regressions between resonance frequency, bedrock depth and VS30 would be implemented into nonlinear site amplification model and further development towards Ground Motion Prediction Equations for Croatia.

ANALISIS TINGKAT RESIKO DAMPAK GEMPABUMI DI KABUPATEN CILACAP MENGGUNAKAN METODE DSHA DAN DATA MIKROTREMOR

Soil mechanical research has been done in Cilacap Regency using DSHA method and microtremor data. This study aims to analyze the local land response to earthquakes based on the dominant frequency parameters (f0), amplification factor (A0), wave velocity VS30 and seismic hazard analysis through deterministic approach. This research uses 193 microtremor measurement points using a short period TDS-303 type (3 component) seismometer. Microtremor data were analyzed using the Horizontal to Vertical Spectral Ratio (HVSR) method in geopsy software. DSHA analysis refers to the source of the Lembang Fault earthquake and Java Subduction zone for deterministic calculations. Based on the analysis of HVSR method, Cilacap Regency is located on land type 1 (frequency 0-1.33 Hz) and soil type 2 (frequency 1,33-5 Hz) according to Kanai Classification (1983), dominated amplification value 1,104 to 8,171 times, then Dominated by soil class E (VS30 value 183 m / s) and soil class D (183 m / s VS30 366 m / s) according to NEHRP Classification (2000). This indicates that Cilacap Regency has high vulnerability to earthquake disaster. Based on the estimated value of PGA calculation method of DSHA, from the calculation of earthquake source Subduction obtained Java PGA bedrock 0,045 g - 0,0671 g and PGA surface rock 0,1926 g - 0,4855 g and calculation of Lembang Fault obtained PGA bedrock 0, 09 g - 0.025 g and PGA surface rocks 0.017 g - 0.089 g. Based on risk map analysis (combination of dominant frequency analysis, amplification, susceptibility factor and ability factor), the highest risk areas are Kec. Adipala, Kasugihan, Binangun, Nusawungun, Cil. Middle, Cil. South, Cil. North, allegedly the soil layer constituent area is a layer of thick and soft sediments. While the low risk of Kec. Majenang and Dayeuh Luhur.

Which is a better proxy, site period or depth to bedrock, in modelling linear site response in addition to the average shear-wave velocity?

This study aims to identify the best-performing site characterization proxy alternative and complementary to the conventional 30 m average shear-wave velocity VS30, as well as the optimal combination of proxies in characterizing linear site response. Investigated proxies include T0 (site fundamental period obtained from earthquake horizontal-to-vertical spectral ratios), VSz (measured average shear-wave velocities to depth z, z = 5, 10, 20 and 30 m), Z0.8 and Z1.0 (measured site depths to layers having shear-wave velocity 0.8 and 1.0 km/s, respectively), as well as Zx-infer (inferred site depths from a regional velocity model, x = 0.8 and 1.0, 1.5 and 2.5 km/s). To evaluate the performance of a site proxy or a combination, a total of 1840 surface-borehole recordings is selected from KiK-net database. Site amplifications are derived using surface-to-borehole response-, Fourier- and cross-spectral ratio techniques and then are compared across approaches. Next, the efficacies of 7 single-proxies and 11 proxy-pairs are quantified based on the site-to-site standard deviation of amplification residuals of observation about prediction using the proxy or the pair. Our results show that T0 is the best-performing single-proxy among T0, Z0.8, Z1.0 and VSz. Meanwhile, T0 is also the best-performing proxy among T0, Z0.8, Z1.0 and Zx-infer complementary to VS30 in accounting for the residual amplification after VS30-correction. Besides, T0 alone can capture most of the site effects and should be utilized as the primary site indicator. Though (T0, VS30) is the best-performing proxy pair among (VS30, T0), (VS30, Z0.8), (VS30, Z1.0), (VS30, Zx-infer) and (T0, VSz), it is only slightly better than (T0, VS20). Considering both efficacy and engineering utility, the combination of T0 (primary) and VS20 (secondary) is recommended. Further study is needed to test the performances of various proxies on sites in deep sedimentary basins.

Theoretical studies on the hydrous lower mantle and D″ layer minerals

The incorporation mechanisms and elastic properties of hydrous Bridgmanite (Brg) and post-Perovskite (PPv) are investigated by using first principles calculations at the lower mantle pressures. The elastic properties calculations in both (Al, Fe)-free and (Al, Fe)-bearing systems give evidences that hydrogen has less effect on the elastic wave velocities and moduli in (Al, Fe)-free and Al-bearing system. However, the elastic wave velocities and moduli, especially the shear velocity VS and the shear modulus G, are remarkably sensitive to the presence of hydrogen in the Fe-bearing system. The calculated shear velocity anomaly (dVS) are −2.9% for Fe3+SiH-Brg and −3.1% for Fe3+SiH-PPv, which are very close to the average anomaly value of LLSVPs. This result may imply the Ferric-bearing hydrous MgSiO3 is likely a dominated mineral in LLSVPs. Density functional perturbation theory (DFPT) and QHA calculation have also been performed to determine the P–T phase diagram for different hydrous systems. The phase transition boundary between Brg and PPv shifts to higher or lower pressures when the hydrogen atom substitutes in the Mg or Si sites in the lattice, respectively. The existence of volatiles such as hydrogen may account for the strong lateral chemical heterogeneity in lowermost mantle.

Differential interferometry, structural lineaments and terrain deformation analysis applied in Zero Zone 2016 Earthquake (Manta, Ecuador)

The earthquake of April 16, 2016 caused huge economic losses and human lives in Ground Zero of the city of Manta, Ecuador. The present study delimited the affected areas by superficial deformation and vertical displacements of the relief in this zone by means of the differential interferometry analysis (DInSAR), with the support of geophysical techniques such as electrical tomography of the subsoil and of georadar in combination with the analysis of concentration of structural lineaments-tectonic deformation, seismicity and geotechnical parameters such as soil liquefaction indexes, cutting wave velocity Vs30, among others. This combination of techniques allowed the spatial location with greater certainty of areas susceptible to seismic risk for construction and related to the soils typology of the Ecuadorian Construction Standard-NEC 2015. This proposed methodology improved forecasting mechanisms for the reduction of seismic risk based on maps of its susceptibility to the possible occurrence of an earthquake of magnitude as that of 16 April 16, 2016. Forecast that can be done to protect engineering works and to the population, especially in tectonically deformed areas.