An approach to construct a Netherlands-wide ground-motion amplification model

2021 ◽  
Author(s):  
Janneke van Ginkel ◽  
Elmer Ruigrok ◽  
Rien Herber
Keyword(s):  
The Netherlands ◽  
Ground Motion ◽  
Seismic Wave ◽  
Transfer Functions ◽  
Site Response ◽  
Data Availability ◽  
Earthquake Ground Motion ◽  
Sediment Layer ◽  
Small Magnitude ◽  
Near Surface

<p>Local site conditions can strongly influence the level of amplification of ground-motion at the surface during an earthquake. Especially near-surface low velocity sediments overlying stiffer seismic bedrock modify earthquake ground motions in terms of amplitudes and frequency content, the so-called site response. Earthquake ground-motion site response is of great concern because it can lead to amplified surface shaking resulting in significant damage on structures despite small magnitude events. The Netherlands has tectonically related seismic activity in the southern region with magnitudes up to 5.8 measured so far. In addition, gas extraction in the Groningen field in the northern part of the Netherlands, is regularly causing shallow (3 km), low magnitude (Mw max= 3.6), induced earthquakes. The shallow geology of the Netherlands consists of a very heterogeneous soft sediment cover, which has a strong effect on seismic wave propagation and in particular on the amplitude of ground shaking.</p><p> </p><p>The ambient seismic field and local earthquakes recorded over 69 borehole stations in Groningen are used to define relationships between the subsurface lithological composition, measured shear-wave velocity profiles, horizontal-to-vertical spectral ratios (HVSR) and empirical transfer functions (ETF). For the Groningen region we show that the HVSR matches the ETF well and conclude that the HVSR can be used as a first proxy for earthquake site-response. In addition, based on the ETFs we observe that most of the seismic wave amplification occurs in the top 50 m of the much thicker sediment layer. Here, a velocity contrast is present between the very soft Holocene clays and peat on top of the stiffer Pleistocene sands.</p><p> </p><p>Based on the learnings from Groningen we first constructed sediment type classes for the Dutch subsurface, each class representing a level of expected amplification. Secondly, the HVSR curves are estimated for all surface seismometers in the Netherlands seismic network and a sediment class is assigned to each location. Highest HVSR peak amplitudes are measured at sites with the highest level of amplification of the sediment classification. Based on this correlation and the presence of a detailed shallow geological model at most sites in the Netherlands, a simplistic approach is presented to predict amplification at any location with sufficient lithologic information. With this approach based on the shallow sediment composition, we can obtain constraints on the seismic hazard in areas that have limited data availability but have potential risk of seismicity, for example due to geothermal energy extraction.</p>

scholarly journals Regional-Scale 3D Ground-Motion Simulations of Mw 7 Earthquakes on the Hayward Fault, Northern California Resolving Frequencies 0–10 Hz and Including Site-Response Corrections

2020 ◽  
Vol 110 (6) ◽  
pp. 2862-2881
Author(s):  
Arthur J. Rodgers ◽  
Arben Pitarka ◽  
Ramesh Pankajakshan ◽  
Bjorn Sjögreen ◽  
N. Anders Petersson
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Regional Scale ◽  
Frequency Resolution ◽  
Earthquake Ground Motion ◽  
Northern California ◽  
Soft Soils ◽  
Near Surface ◽  
Ground Motion Simulations ◽  
Scenario Earthquakes

ABSTRACT Large earthquake ground-motion simulations in 3D Earth models provide constraints on site-specific shaking intensities but have suffered from limited frequency resolution and ignored site response in soft soils. We report new regional-scale 3D simulations for moment magnitude 7.0 scenario earthquakes on the Hayward Fault, northern California with SW4. Simulations resolved significantly broader band frequencies (0–10 Hz) than previous studies and represent the highest resolution simulations for any such earthquake to date. Seismic waves were excited by a kinematic rupture following Graves and Pitarka (2016) and obeyed wave propagation in a 3D Earth model with topography from the U.S. Geological Survey (USGS) assuming a minimum shear wavespeed, VSmin, of 500  m/s. We corrected motions for linear and nonlinear site response for the shear wavespeed, VS, from the USGS 3D model, using a recently developed ground-motion model (GMM) for Fourier amplitude spectra (Bayless and Abrahamson, 2018, 2019a). At soft soil locations subjected to strong shaking, the site-corrected intensities reflect the competing effects of linear amplification by low VS material, reduction of stiffness during nonlinear deformation, and damping of high frequencies. Sites with near-surface VS of 500  m/s or greater require no linear site correction but can experience amplitude reduction due to nonlinear response. Averaged over all sites, we obtained reasonable agreement with empirical ergodic median GMMs currently used for seismic hazard and design ground motions (epsilon less than 1), with marked improvement at soft sedimentary sites. At specific locations, the simulated shaking intensities show systematic differences from the GMMs that reveal path and site effects not captured in these ergodic models. Results suggest how next generation regional-scale earthquake simulations can provide higher spatial and frequency resolution while including effects of soft soils that are commonly ignored in scenario earthquake ground-motion simulations.

scholarly journals Development of a seismic site-response zonation map for the Netherlands

2022 ◽  
Vol 22 (1) ◽  
pp. 41-63
Author(s):  
Janneke van Ginkel ◽  
Elmer Ruigrok ◽  
Jan Stafleu ◽  
Rien Herber
Keyword(s):  
The Netherlands ◽  
Seismic Hazard ◽  
Transfer Functions ◽  
Site Response ◽  
Empirical Relationship ◽  
Ambient Vibration ◽  
Induced Earthquakes ◽  
Near Surface ◽  
Zonation Map ◽  
Moderate Seismicity

Abstract. Earthquake site response is an essential part of seismic hazard assessment, especially in densely populated areas. The shallow geology of the Netherlands consists of a very heterogeneous soft sediment cover, which has a strong effect on the amplitude of ground shaking. Even though the Netherlands is a low- to moderate-seismicity area, the seismic risk cannot be neglected, in particular, because shallow induced earthquakes occur. The aim of this study is to establish a nationwide site-response zonation by combining 3D lithostratigraphic models and earthquake and ambient vibration recordings. As a first step, we constrain the parameters (velocity contrast and shear-wave velocity) that are indicative of ground motion amplification in the Groningen area. For this, we compare ambient vibration and earthquake recordings using the horizontal-to-vertical spectral ratio (HVSR) method, borehole empirical transfer functions (ETFs), and amplification factors (AFs). This enables us to define an empirical relationship between the amplification measured from earthquakes by using the ETF and AF and the amplification estimated from ambient vibrations by using the HVSR. With this, we show that the HVSR can be used as a first proxy for site response. Subsequently, HVSR curves throughout the Netherlands are estimated. The HVSR amplitude characteristics largely coincide with the in situ lithostratigraphic sequences and the presence of a strong velocity contrast in the near surface. Next, sediment profiles representing the Dutch shallow subsurface are categorised into five classes, where each class represents a level of expected amplification. The mean amplification for each class, and its variability, is quantified using 66 sites with measured earthquake amplification (ETF and AF) and 115 sites with HVSR curves. The site-response (amplification) zonation map for the Netherlands is designed by transforming geological 3D grid cell models into the five classes, and an AF is assigned to most of the classes. This site-response assessment, presented on a nationwide scale, is important for a first identification of regions with increased seismic hazard potential, for example at locations with mining or geothermal energy activities.

scholarly journals Development of a country-wide seismic site-response zonation map for the Netherlands

2021 ◽  
Author(s):  
Janneke van Ginkel ◽  
Elmer Ruigrok ◽  
Jan Stafleu ◽  
Rien Herber
Keyword(s):  
The Netherlands ◽  
Seismic Hazard ◽  
Site Response ◽  
Empirical Relationship ◽  
Ambient Vibration ◽  
Ratio Method ◽  
Small Magnitude ◽  
Near Surface ◽  
Zonation Map ◽  
Moderate Seismicity

Abstract. Earthquake site-response is an essential part of seismic hazard assessment, especially in densely populated areas. The shallow geology of the Netherlands consists of a very heterogeneous soft sediment cover, which has a strong effect on seismic wave propagation and in particular on the amplitude of ground shaking, resulting in significant damage on structures despite the fact that the events are of small magnitude. Even though it is a low-to-moderate seismicity area, the seismic risk cannot be neglected, in particular, because shallow induced earthquakes occur. The aim of this study is to establish a nationwide site-response zonation by using the lithostratigraphy, earthquake- and ambient vibration recordings. In the first step, we constrain the parameters (velocity contrast and shear-wave velocity) that are indicative of ground-motion amplification in the Groningen area. For this, we combine ambient vibration and earthquake recordings using resp. the horizontal-to-vertical spectral ratio method (HVSR), borehole empirical transfer functions (ETFs) and amplification factors (AFs). This enables us to define an empirical relationship between measured earthquake amplification from the ETF and AF, and amplification estimated with the HVSR derived from the ambient seismic field. Therewith, we show that the HVSR can be used as a first proxy for amplification. Subsequently, HVSR curves throughout the Netherlands are estimated. The resulting peak amplitudes largely coincide with the in-situ lithostratigraphic sequences and the presence of a strong velocity contrast in the near-surface. Next, sediment profiles representing the Dutch shallow subsurface are categorized into five classes, where each class is representing a level of expected amplification. The mean amplification for each class, and its variability, is quantified using 66 sites with measured earthquake amplification (ETF and AF) and 115 sites with HVSR curves. The site-response (amplification) zonation map for the Netherlands is designed by transforming published geological 3D grid cell models into the five classes and an AF is assigned to most of the classes. This presented site-response assessment on a national scale is important for a first identification of regions with increased seismic hazard potential, for example at locations with mining or geothermal energy activities.

scholarly journals Basin Resonance and Seismic Hazard for Jakarta, Indonesia

2018 ◽  
Author(s):  
Athanasius Cipta ◽  
Phil Cummins ◽  
Masyhur Irsyam ◽  
Sri Hidayati
Keyword(s):  
Ground Motion ◽  
Seismic Waves ◽  
Response Spectrum ◽  
Capital City ◽  
Earthquake Ground Motion ◽  
Computational Domain ◽  
Near Surface ◽  
Earthquake Scenario ◽  
Design Response Spectrum ◽  
Intraslab Earthquake

We use earthquake ground motion modelling via Ground Motion Prediction Equations (GMPEs) and numerical simulation of seismic waves to consider the effects of site amplification and basin resonance in Jakarta, the capital city of Indonesia. While spectral accelerations at short periods are sensitive to near-surface conditions (i.e., Vs30), our results suggest that, for basins as deep as Jakarta’s, available GMPEs cannot be relied upon to accurately estimate the effect of basin depth on ground motions at long periods (>1 s). Amplitudes at such long periods are influenced by entrapment of seismic waves in the basin, resulting in longer duration of strong ground motion, and interference between incoming and reflected waves as well as focusing at basin edges may amplify seismic waves. In order to simulate such phenomena in detail, a basin model derived from a previous study is used as a computational domain for deterministic earthquake scenario modeling in a 2-dimensional cross-section. A Mw 9.0 megathrust, a Mw 6.5 crustal thrust and a Mw 7.0 instraslab earthquake are chosen as scenario events that pose credible threats to Jakarta, and the interactions with the basin of seismic waves generated by these events were simulated. The highest PGV amplifications are recorded at sites near the middle of the basin and near its southern edge, with maximum amplifications of PGV in the horizontal component of 200% for the crustal, 600% for the megathrust and 335% for the deep intraslab earthquake scenario, respectively. We find that the levels of ground motion response spectral acceleration fall below those of the 2012 Indonesian building Codes's design response spectrum for short periods (< 1 s), but closely approach or may even exceed these levels for longer periods.

Repeatable Source, Path, and Site Effects from the 2019 M 7.1 Ridgecrest Earthquake Sequence

2020 ◽  
Vol 110 (4) ◽  
pp. 1530-1548 ◽  
Author(s):  
Grace A. Parker ◽  
Annemarie S. Baltay ◽  
John Rekoske ◽  
Eric M. Thompson
Keyword(s):  
Los Angeles ◽  
Ground Motion ◽  
Site Response ◽  
Ground Motions ◽  
Warning System ◽  
Site Amplification ◽  
Earthquake Sequence ◽  
Ground Acceleration ◽  
Small Magnitude ◽  
Earthquake Early Warning System

ABSTRACT We use a large instrumental dataset from the 2019 Ridgecrest earthquake sequence (Rekoske et al., 2019, 2020) to examine repeatable source-, path-, and site-specific ground motions. A mixed-effects analysis is used to partition total residuals relative to the Boore et al. (2014; hereafter, BSSA14) ground-motion model. We calculate the Arias intensity stress drop for the earthquakes and find strong correlation with our event terms, indicating that they are consistent with source processes. We look for physically meaningful trends in the partitioned residuals and test the ability of BSSA14 to capture the behavior we observe in the data. We find that BSSA14 is a good match to the median observations for M>4. However, we find bias for individual events, especially those with small magnitude and hypocentral depth≥7  km, for which peak ground acceleration is underpredicted by a factor of 2.5. Although the site amplification term captures the median site response when all sites are considered together, it does not capture variations at individual stations across a range of site conditions. We find strong basin amplification in the Los Angeles, Ventura, and San Gabriel basins. We find weak amplification in the San Bernardino basin, which is contrary to simulation-based findings showing a channeling effect from an event with a north–south azimuth. This and an additional set of ground motions from earthquakes southwest of Los Angeles suggest that there is an azimuth-dependent southern California basin response related to the orientation of regional structures when ground motion from waves traveling south–north are compared with those in the east–west direction. These findings exhibit the power of large, spatially dense ground-motion datasets and make clear that nonergodic models are a way to reduce bias and uncertainty in ground-motion estimation for applications like the U.S. Geological Survey National Seismic Hazard Model and the ShakeAlert earthquake early warning System.

Micro-Tremor Data Analysis for Site Response Studies of Srinagar, Garhwal (India)

2019 ◽  
Vol 10 (2) ◽  
pp. 69-83
Author(s):  
Pradeep Kumar Singh Chauhan ◽  
Abha Mittal ◽  
Gayatri Devi ◽  
Anirudh Singh
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Soft Soil ◽  
Seismic Hazard Assessment ◽  
Vulnerability Index ◽  
Earthquake Ground Motion ◽  
Seismic Zone ◽  
Noise Data ◽  
Thick Overburden ◽  
The City

Site response studies using micro-tremor or ambient noise data are one of the well-known tools of seismic hazard assessment and microzonation. Different soil types behave differently for the same ground motion - some amplify it and some do not. It is well-accepted that, besides the earthquake magnitude and epicenter distance, local geology exerts significant influence on earthquake ground motion at a given location. In general, soft soil and thick overburden amplify the ground motion. Micro-tremor data provides an important input in seismic microzonation studies. Srinagar (Garhwal Himalaya), the largest growing city of Uttarakhand, India, lies in seismic zone V and has long seismic history. The micro-tremor data using Altus K2SMA has been collected from 47 locations in different parts of the city. The city has been divided into three zones on the basis of natural frequency (Nf). The most part of the city lies in zone 1. The central part of the city has a share of rest zones i.e. II and III. Vulnerability index has been also computed and found in the range from 1–236.

Developing an integrated 3D geological-seismological model at urban scale in Basel, Switzerland

2021 ◽  
Author(s):  
Afifa Imtiaz ◽  
Francesco Panzera ◽  
Miroslav Hallo ◽  
Horst Dresmann ◽  
Brian Steiner ◽  
...  
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Dispersion Curves ◽  
Ambient Vibration ◽  
Unconsolidated Sediments ◽  
Earthquake Ground Motion ◽  
Model Parameters ◽  
Swiss Canton ◽  
Geological Conditions ◽  
Seismological Model

<p>Assessment of seismic risk at a local scale is fundamental to the adoption of efficient risk mitigation strategies for urban areas with spatially distributed building portfolios and infrastructure systems. An important component of such a study is to estimate the spatial distribution of the expected seismic ground motion induced by site response. The current work presents a detailed seismic site response study at urban scale, performed in the context of developing an earthquake risk model for the Swiss canton of Basel-Stadt. Different studies undertaken over last two decades in the area concluded that unconsolidated sediments were responsible for inducing resonances and significant amplification of seismic waves over a range of frequencies pertinent to engineering interest. Therefore, we make a step forward in this study by attempting to develop a three-dimensional (3D) integrated geological-seismological model, which will explicitly account for the complex geological conditions at the surface and at depth. Thanks to the past projects, there is an abundance of geological, geophysical and seismological data for Basel. Earthquake recordings are available from an operating network of more than 20 permanent stations as well as from several former and six current temporary stations. Ambient noise measurements are available from several hundred single stations and more than 25 passive seismic arrays. In addition, a number of active seismic measurements and borehole logs are also available. An updated 3D model of subsurface geological structure of the area has been provided by the team of Applied and Environmental Geology (AUG) of University of Basel.</p><p>We use dispersion characteristics of surface waves from ambient vibration array data for imaging subsurface shear wave velocity (Vs) profiles. We apply a novel approach based on a Multizonal Transdimensional Inversion (MTI), formulated in the Bayesian probabilistic framework, in order to retrieve 1D Vs profiles from ambient vibration arrays. A joint inversion of multimodal Rayleigh and Love wave dispersion curves along with Rayleigh wave ellipticity curve is performed. This is a major improvement as such joint inversions were performed only for few sites in this area. The key advantages of MTI are that the model complexity in terms of number of layers and distribution of associated parameters are determined self-adaptively from the measured data, and model uncertainties can be assessed quantitatively. Additional constraints on the depths of intermediate layers are drawn from the 3D geological model and boreholes for the multizonal inversion. Moreover, the solution of the transdimensional Bayesian inversion enables reconstruction of the posterior probability density function of prior model parameters and their properties from the ensemble of inverted models. Hence, the model uncertainty can be duly propagated from dispersion curves to Vs profiles. The initial results seem very promising in resolving the interfaces corresponding to major velocity contrasts, especially in the complex sedimentary structure of the Rhine Graben formation. The ongoing analysis will also better identify composition, geometry, thickness and topography of the surficial unconsolidated sediments as well as the underlying more consolidated layers, which will form the basis for future numerical simulations of earthquake ground motion.</p>

Seismic Wave Propagation and Basin Amplification in the Wasatch Front, Utah

2021 ◽  
Author(s):  
Morgan P. Moschetti ◽  
David Churchwell ◽  
Eric M. Thompson ◽  
John M. Rekoske ◽  
Emily Wolin ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Ground Motion ◽  
Seismic Wave ◽  
Seismic Velocity ◽  
Site Response ◽  
Ground Motions ◽  
Seismic Wave Propagation ◽  
Velocity Models ◽  
Ground Motion Variability ◽  
Wasatch Front

Abstract Ground-motion analysis of more than 3000 records from 59 earthquakes, including records from the March 2020 Mw 5.7 Magna earthquake sequence, was carried out to investigate site response and basin amplification in the Wasatch Front, Utah. We compare ground motions with the Bayless and Abrahamson (2019; hereafter, BA18) ground-motion model (GMM) for Fourier amplitude spectra, which was developed on crustal earthquake records from California and other tectonically active regions. The Wasatch Front records show a significantly different near-source rate of distance attenuation than the BA18 model, which we attribute to differences in (apparent) geometric attenuation. Near-source residuals show a period dependence of this effect, with greater attenuation at shorter periods (T<0.5  s) and a correlation between period and the distance over which the discrepancy manifests (∼20–50  km). We adjusted the recorded ground motions for these regional path effects and solved for station site terms using linear mixed-effects regressions, with groupings for events and stations. We analyzed basin amplification by comparing the site terms with the basin geometry and basin depths from two seismic-velocity models for the region. Sites over the deeper parts of the sedimentary basins are amplified by factors of 3–10, relative to sites with thin sedimentary cover, with greater amplification at longer periods (T≳1  s). Average ground-motion variability increases with period, and long-period variability exhibits a slight increase at the basin edges. These results indicate regional seismic wave propagation effects requiring further study, and potentially a regionalized GMM, as well as highlight basin amplification complexities that may be incorporated into seismic hazard assessments.

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