scholarly journals Sediment-induced amplification in the Northeastern United States: A case study in Providence, Rhode Island

1995 ◽  
Vol 85 (5) ◽  
pp. 1388-1397
Author(s):  
Karen M. Fischer ◽  
Lynn A. Salvati ◽  
Susan E. Hough ◽  
Edward Gonzalez ◽  
Chad E. Nelsen ◽  
...  
Keyword(s):  
Ground Motion ◽  
Rhode Island ◽  
Site Response ◽  
P Wave ◽  
Earthquake Ground Motion ◽  
Soft Sediment ◽  
Spectral Ratios ◽  
Study Region ◽  
Entire Study ◽  
Sediment Layers

Abstract We employed ambient-noise measurements to assess the potential for seismic site response in sediment-filled valleys that intersect beneath downtown Providence, Rhode Island. At eight valley stations and at two sites on an adjacent bedrock highland, we recorded ground motion from two types of sources: pile drivers at a local construction site and ambient microtremors. At all valley sites where sediment thicknesses exceed 10 m, spectral ratios contain amplitude peaks at frequencies of 1.5 to 3.0 Hz. In contrast, spectral ratios from the two sites on the bedrock highland where sediment cover is less than 4-m thick are relatively flat within this frequency range. A variety of borehole logs identified two fundamental sediment types (soft sediment and a consolidated glacial till) and were used to map layer thicknesses over the entire study region. Refraction data constrained P-wave velocity in the bedrock to be 3680 ± 160 m/sec and indicated two soft-sediment layers with P-wave velocities of 300 ± 50 and 1580 ± 120 m/sec. Using a one-dimensional reflection matrix technique, we matched the spectral-ratio peak observed at each valley site with the frequency of fundamental resonance predicted for local layer thicknesses and velocities. A positive correlation between the best-fitting soft-sediment velocities and bedrock depth may reflect greater compaction in the deepest sediments or a locally two-dimensional sediment resonance at the deepest sediment sites. We conclude that unconsolidated sediment layers under downtown Providence have the potential to amplify earthquake ground motion at frequencies damaging to engineered structures.

Feasibility of the use of Microtremors in Estimating Site Response during Earthquakes: Some Test Cases in Italy

1991 ◽  
Vol 7 (4) ◽  
pp. 551-561 ◽  
Author(s):  
Antonio Rovelli ◽  
Shri K. Singh ◽  
Luca Malagnini ◽  
Alessandro Amato ◽  
Massimo Cocco
Keyword(s):  
Ground Motion ◽  
Seismic Waves ◽  
Site Response ◽  
Spectral Ratio ◽  
Test Cases ◽  
Spectral Ratios ◽  
Cultural Noise ◽  
Maximum Amplification

We explore the feasibility of the use of microtremors in estimating the amplification of seismic waves at soft sites in Italy. Microtremors were measured at three soft sites and nearby hard sites at night when the cultural noise was minimum. These soft sites were selected as those showing the largest amplifications of ground motion during earthquakes as compared to the records on the hard sites or with respect to the predicted spectra. We compare the soft-to-hard site microtremor spectral ratios with the corresponding acceleration spectral ratios. A rough estimate of the shape and level of spectral amplification is obtained from the microtremor data in all three cases. However, the details of the soft-to-hard site spectral ratio are not reproduced and some differences appear in (a) the frequency at which the maximum amplification occurs, and (b) the bandwidth of the significant amplification. More testing of the method is needed before its wider use for microzonation in Italy can be recommended.

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.

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.

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>

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>

The basin effect and liquefaction in the catastrophe models: Case study – Vancouver region, Canada

2020 ◽  
Author(s):  
Svetlana Stripajova ◽  
Peter Pazak ◽  
Jan Vodicka ◽  
Goran Trendafiloski
Keyword(s):  
Ground Motion ◽  
Sedimentary Basin ◽  
Water Saturation ◽  
Site Response ◽  
Earthquake Ground Motion ◽  
Soil Conditions ◽  
Liquefaction Hazard ◽  
Geological Conditions ◽  
Catastrophe Models

<p>The presence of thick soft alluvial sediment-filled basins, like in river’s deltas, can significantly amplify and prolongate the earthquake ground motion. Moreover, the high-water saturation of such soft sediments and cyclic earthquake loading can lead to liquefaction. The basin and liquefaction effect can contribute to substantial modification of the seismic motion and increase of the potential losses at a particular location. Well-known examples of such high financial losses during earthquakes for basin effect is Mw 8.1 Mexico City 1985 and for liquefaction is Darfield and Christchurch earthquakes series in 2010 and 2011. Thus, the quantification of these effects is particularly important for the current underwriting products and the industry requires their further detailed consideration in the catastrophe models and pricing approaches. Impact Forecasting, Aon’s catastrophe model development center of excellence, has been committed to help (re)insurers on that matter.</p><p>This paper presents case study of the quantification of the basin effect and liquefaction for Vancouver region, Canada for specific scenario Mw 7.5 Strait of Georgia crustal earthquake. The southern part of the Vancouver region is located on a deep sedimentary basin created in the Fraser River delta. In case of deep Vancouver sedimentary basin considering amplification only due to shallow site response Vs30-dependent site term is not sufficient. Therefore, we derived (de)amplification function for different periods to quantify basin effect. We used NGA – West 2 ground motion prediction equations (GMPEs) for crustal events which include basin depth term. Amplification function was derived with respect to standard GMPEs for crustal events in western Canada. Amplification, considering site response including Vs30 and basin depth term at period 0.5 s can reach values as high as 3 at the softest and deepest sediments. The liquefaction potential was based on HAZUS and Zhu et al. (2017) methodologies calibrated to better reflect local geological conditions and liquefaction observations (Monahan et al. 2010, Clague 2002). We used USGS Vs30 data, enhanced by local seismic and geologic measurements, to characterize soil conditions, and topographical data and IF proprietary flow accumulation data to characterize water saturation. Liquefaction hazard is calculated in terms of probability of liquefaction occurrence and permanent ground deformation. For the chosen scenario the potential contribution to mean loss due to basin effect could be in the range 15% - 30% and 35% - 75% due to liquefaction depending on structural types of the buildings.</p>

scholarly journals A review on the multi-criteria seismic hazard analysis of Ethiopia: with implications of infrastructural development

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Alemayehu Ayele ◽  
Kifle Woldearegay ◽  
Matebie Meten
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Active Fault ◽  
Site Response ◽  
Seismic Hazard Assessment ◽  
Earthquake Ground Motion ◽  
Response Analysis ◽  
Ethiopian Rift ◽  
Rift System ◽  
Main Ethiopian Rift

AbstractEarthquake is a sudden release of energy due to faults. Natural calamities like earthquakes can neither be predicted nor prevented. However, the severity of the damages can be minimized by development of proper infrastructure which includes microzonation studies, appropriate construction procedures and earthquake resistant designs. The earthquake damaging effect depends on the source, path and site conditions. The earthquake ground motion is affected by topography (slope, hill, valley, canyon, ridge and basin effects), groundwater and surface hydrology. The seismic hazard damages are ground shaking, structural damage, retaining structure failures and lifeline hazards. The medium to large earthquake magnitude (< 6) reported in Ethiopia are controlled by the main Ethiopian rift System. The spatial and temporal variation of earthquake ground motion should be addressed using the following systematic methodology. The general approaches used to analyze damage of earthquake ground motions are probabilistic seismic hazard assessment (PSHA), deterministic seismic hazard assessment (DSHA) and dynamic site response analysis. PSHA considers all the scenarios of magnitude, distance and site conditions to estimate the intensity of ground motion distribution. Conversely, DSHA taken into account the worst case scenarios or maximum credible earthquake to estimate the intensity of seismic ground motion distribution. Furthermore, to design critical infrastructures, DSHA is more valuable than PSHA. The DSHA and PSHA ground motion distributions are estimated as a function of earthquake magnitude and distance using ground motion prediction equations (GMPEs) at top of the bedrock. Site response analysis performed to estimate the ground motion distributions at ground surface using dynamic properties of the soils such as shear wave velocity, density, modulus reduction, and material damping curves. Seismic hazard evaluation of Ethiopia shown that (i) amplification is occurred in the main Ethiopian Rift due to thick soil, (ii) the probability of earthquake recurrence due to active fault sources. The situation of active fault is oriented in the N-S direction. Ethiopia is involved in huge infrastructural development (including roads, industrial parks and railways), increasing population and agricultural activity in the main Ethiopian Rift system. In this activity, socio-economic development, earthquake and earthquake-generated ground failures need to be given attention in order to reduce losses from seismic hazards and create safe geo-environment.

NGA-subduction global ground motion models with regional adjustment factors

2021 ◽  
pp. 875529302110348
Author(s):  
Grace A Parker ◽  
Jonathan P Stewart ◽  
David M Boore ◽  
Gail M Atkinson ◽  
Behzad Hassani
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Peak Ground Velocity ◽  
Earthquake Ground Motion ◽  
Motion Models ◽  
Magnitude Scaling ◽  
Aleatory Variability ◽  
Single Station ◽  
Ground Motion Models

We develop semi-empirical ground motion models (GMMs) for peak ground acceleration, peak ground velocity, and 5%-damped pseudo-spectral accelerations for periods from 0.01 to 10 s, for the median orientation-independent horizontal component of subduction earthquake ground motion. The GMMs are applicable to interface and intraslab subduction earthquakes in Japan, Taiwan, Mexico, Central America, South America, Alaska, the Aleutian Islands, and Cascadia. The GMMs are developed using a combination of data inspection, data regression with respect to physics-informed functions, ground-motion simulations, and geometrical constraints for certain model components. The GMMs capture observed differences in source and path effects for interface and intraslab events, conditioned on moment magnitude, rupture distance, and hypocentral depth. Site effect and aleatory variability models are shared between event types. Regionalized GMM components include the model constant (that controls ground motion amplitude), anelastic attenuation, magnitude-scaling break point, linear site response, and sediment depth terms. We develop models for the aleatory between-event variability [Formula: see text], within-event variability [Formula: see text], single-station within-event variability [Formula: see text], and site-to-site variability [Formula: see text]. Ergodic analyses should use the median GMM and aleatory variability computed using the between-event and within-event variability models. An analysis incorporating non-ergodic site response should use the median GMM at the reference shear-wave velocity condition, a site-specific site response model, and aleatory variability computed using the between-event and single-station within-event variability models. Epistemic uncertainty in the median model is represented by standard deviations on the regional model constants, which facilitates scaled-backbone representations of model uncertainty in hazard analyses.

Site Response in Providence, Rhode Island: Constraints from Ambient Noise Measurements

1992 ◽  
Vol 63 (4) ◽  
pp. 525-532 ◽  
Author(s):  
K. M. Fischer ◽  
S. E. Hough
Keyword(s):  
Rhode Island ◽  
Ambient Noise ◽  
Site Response ◽  
Seismic Refraction ◽  
Frequency Spectra ◽  
Noise Measurements ◽  
Island Constraints ◽  
Seismic Refraction Data ◽  
Sediment Layers ◽  
River Valleys

Abstract We conducted an ambient noise survey to assess the potential for seismic site response in Providence, Rhode Island. Providence is built on bedrock valleys that are partially filled with unconsolidated Holocene sediments. Because similar valley structures exist in other heavily populated coastal and river cities of the northeastern United States, the results of this study are relevant to seismic hazards throughout the region. At sites located in the river valleys beneath downtown Providence, we found peaks in ambient noise frequency spectra that suggest amplification of energy in the range of 2–3 Hz. This spectral peak occurs in the spectra from sediment sites and in spectral ratios that reference sediment to hardrock stations. We used geotechnical borehole records to constrain valley structure and seismic refraction data to determine bedrock velocity, and we calculated the theoretical response to ground motion for one-dimensional models that approximate basin structure. The modeling shows that the 2–3 Hz ambient noise peak can be interpreted as the fundamental resonance frequency of low-impedance surface sediment layers.

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