Nonlinear Site Effects from the 30 November 2018 Anchorage, Alaska, Earthquake

2021 ◽  
Author(s):  
John D. Thornley ◽  
Utpal Dutta ◽  
John Douglas ◽  
Zhaohui (Joey) Yang
Keyword(s):  
Site Response ◽  
Strong Motion ◽  
North American Plate ◽  
Peak Ground Velocity ◽  
Reference Station ◽  
Earthquake Hazards ◽  
Ground Acceleration ◽  
Nonlinear Site Response ◽  
Generalized Inversion Technique ◽  
Versus Peak

ABSTRACT Anchorage, Alaska, is a natural laboratory for recording strong ground motions from a variety of earthquake sources. The city is situated in a tectonic region that includes the interface and intraslab earthquakes related to the subducting Pacific plate and crustal earthquakes from the upper North American plate. The generalized inversion technique was used with a local rock reference station to develop site response at >20 strong-motion stations in Anchorage. A database of 94 events recorded at these sites from 2005 to 2019 was also compiled and processed to compare their site response with those in the 2018 Mw 7.1 event (main event). The database is divided into three datasets, including 75 events prior to the main event, the main event, and 19 aftershocks. The stations were subdivided into the site classes defined in the National Earthquake Hazards Reduction Program based on estimated average shear-wave velocity in of the upper 30 m (VS30), and site-response results from the datasets were compared. Nonlinear site response was observed at class D and DE sites (VS30 of 215–300 and 150–215  m/s, respectively) but not at class CD and C sites (VS30 of 300–440 and 440–640  m/s, respectively). The relationship of peak ground acceleration versus peak ground velocity divided by VS30 (shear-strain proxy) was shown to further support the observation that sites with lower VS30 experienced nonlinear site response.

A Ground-Motion Prediction Model for Shallow Crustal Earthquakes in Greece

2020 ◽  
Author(s):  
David M. Boore ◽  
Jonathan P. Stewart ◽  
Andreas A. Skarlatoudis ◽  
Emel Seyhan ◽  
Basil Margaris ◽  
...  
Keyword(s):  
Prediction Model ◽  
Ground Motion ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Peak Ground Velocity ◽  
Motion Prediction ◽  
Ground Motion Prediction ◽  
Ground Acceleration ◽  
Magnitude Scaling ◽  
Nonlinear Site Response

ABSTRACT Using a recently completed database of uniformly processed strong-motion data recorded in Greece, we derive a ground-motion prediction model (GMPM) for horizontal-component peak ground velocity, peak ground acceleration, and 5% damped pseudoacceleration response spectra, at 105 periods ranging from 0.01 to 10 s. The equations were developed by modifying a global GMPM, to account for more rapid attenuation and weaker magnitude scaling in the Greek ground motions than in the global GMPM. Our GMPM is calibrated using the Greek data for distances up to 300 km, magnitudes from 4.0 to 7.0, and time-averaged 30 m shear-wave velocities from 150 to 1200  m/s. The GMPM has important attributes for hazard applications including magnitude scaling that extends the range of applicability to M 8.0 and nonlinear site response. These features are possible because they are well constrained by data in the global GMPM from which our model is derived. An interesting feature of the Greek data, also observed previously in studies of mid-magnitude events (6.1–6.5) in Italy, is that they are substantially overpredicted by the global GMPM, which may be a repeatable regional feature, but may also be influenced by soil–structure interaction. This bias is an important source of epistemic uncertainty that should be considered in hazard analysis.

scholarly journals Source and strong-motion characteristics of two M > 6 buried earthquakes in southwest Taiwan

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Yi-Ying Wen ◽  
Yin-Tung Yen ◽  
Chun-Hsiang Kuo ◽  
Kuo‐En Ching
Keyword(s):  
Velocity Structure ◽  
Site Response ◽  
High Stress ◽  
Fluid Pressure ◽  
Strong Motion ◽  
Peak Ground Velocity ◽  
Rupture Directivity ◽  
Motion Generation ◽  
Nonlinear Site Response ◽  
Layer Region

Abstract We used near-field strong-motion data to investigate the complex combination of source effect and site response for two recent disastrous earthquakes in southwest Taiwan. We estimated strong-motion generation areas (SMGAs) of 2.8 km × 2.8 km and 6.0 km × 4.2 km in a frequency band of 0.4–10 Hz for the 2010 Jiashian and 2016 Meinong earthquakes, respectively. The high-stress drops of 26.2 and 17.0 MPa for these two buried events were potentially related to the small dimension and deep rupture. Our results revealed that both earthquakes exhibited westward rupture directivity, whereas the 2016 Meinong event exhibited a stronger directivity effect because of the consistency between the propagation and slip directions. The localized high peak ground velocity (PGV) patch and the nonlinear site response could be attributed to the soft sediment with high pore fluid pressure and low-velocity structure beneath this region. However, the greater seismic moment and closer faulting location to the thick-mudstone-layer region for the 2016 Meinong event reinforced the strong ground shaking and serious damage over the broad area. This implies that this thick-mudstone-layer region in southern Taiwan plays a crucial role in earthquake response, and an investigation of characteristic site effects should be conducted for seismic hazard mitigation. Graphic abstract

Comparison of Equivalent Linear and Nonlinear Site Response Analysis Results and Model to Estimate Maximum Shear Strain

2016 ◽  
Vol 32 (3) ◽  
pp. 1867-1887 ◽  
Author(s):  
Brian Carlton ◽  
Kohji Tokimatsu
Keyword(s):  
Shear Strain ◽  
Site Response ◽  
Response Spectrum ◽  
Peak Ground Velocity ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Ground Acceleration ◽  
Maximum Shear Strain ◽  
Nonlinear Site Response ◽  
Equivalent Linear

We compared the results of equivalent linear (ELA) and nonlinear site response analyses (NLA) and found that the differences between the values of the peak ground acceleration ( PGA), peak ground velocity ( PGV), Arias intensity ( I a), significant duration ( D5–75), and response spectrum for periods between 0.025 s and 2 s predicted by each method are non-negligible for maximum shear strain values predicted by ELA ( γ max, ELA) greater than 0.04% to 1.0%. As γ max, ELA increases, ELA in general predict smaller shear strain and D5–75 values, and larger PGA, PGV, I a, mean period, and response spectral values for periods less than 0.1 s and periods near the natural site period than NLA. To help researchers and practitioners decide when to use ELA and/or NLA, we developed a model to estimate γ max, ELA before conducting a site response analysis.

Testing Nonlinear Amplification Factors of Ground-Motion Models

2021 ◽  
Author(s):  
Karina Loviknes ◽  
Sreeram Reddy Kotha ◽  
Fabrice Cotton ◽  
Danijel Schorlemmer
Keyword(s):  
Ground Motion ◽  
Nonlinear Models ◽  
Site Response ◽  
Strong Motion ◽  
Site Amplification ◽  
Building Codes ◽  
Linear Amplification ◽  
Ground Acceleration ◽  
Nonlinear Site Response ◽  
The Impact

ABSTRACT We explore nonlinear site effects in the new Japanese ground-motion dataset compiled by Bahrampouri et al. (2020). Following the approach of Seyhan and Stewart (2014), we evaluate the decrease of soil amplification according to the increasing and corresponding ground motion on surface rock (VS30=760  m/s). To better predict the rock ground motion associated with each record, we take into account the between-event variability of the ground motion, and to better evaluate the impact of nonlinearity, we correct observed ground motion on soil by the site-specific linear amplification. Instead of grouping the stations by site-response proxy, we focus on individual stations with several strong-motion records. We develop a framework to test recently published nonlinear site amplification models against a linear site amplification model and compare the results with recent building codes that include nonlinearity. The results show that the site response varies greatly from site to site, indicating that conventional site proxies, such as VS30, are not sufficient to characterize nonlinear site response. Out of all of the Kiban–Kyoshin network stations, 20 stations are selected as having recorded sufficient data to be used in the test. Out of these 20 stations, five stations show signs of nonlinearity, that is, the nonlinear models performed better than the linear-amplification model for all periods T. For most sites, however, the linear site amplification models get the best score. This suggest that, for the range of predicted rock motion considered in this study (peak ground acceleration <0.2g), nonlinearity may not have a sufficiently large impact on soil ground motion to justify the use of nonlinear site terms in ground-motion functional forms and seismic building codes for such moderate-level shaking.

Analysis of Damage to Steel Gas Pipelines Caused by Ground Shaking Effects during the Chi-Chi, Taiwan, Earthquake

2004 ◽  
Vol 20 (4) ◽  
pp. 1095-1110 ◽  
Author(s):  
Howard Hwang ◽  
Yi-Huei Chiu ◽  
Wei-Yao Chen ◽  
Ban-Jwu Shih
Keyword(s):  
Seismic Vulnerability ◽  
Strong Motion ◽  
Peak Ground Velocity ◽  
Gas Pipelines ◽  
Arias Intensity ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
Natural Gas Pipelines ◽  
Taiwan Earthquake ◽  
Vulnerability Functions

This paper presents an investigation on damage to natural gas pipelines in Taichung City from the Chi-Chi Taiwan earthquake. This paper addresses damage due to ground shaking effects and does not address damage due to large ground deformations. Four parameters, that is, peak ground acceleration, peak ground velocity, Arias intensity, and spectral intensity, are used to represent ground shaking. Based on pipe repair data and recorded strong motion data, regression analyses of pipe repair rates were carried out to develop seismic vulnerability functions. From the regression analysis results, Arias intensity is considered as the best parameter for the derivation of seismic vulnerability function. The seismic vulnerability functions derived in this study are for steel gas pipelines with mechanical joints and the pipelines are located in firm soils and in the footwall area subject to ground shaking from an earthquake caused by a thrust fault.

Site Amplification at Permanent Stations in Northeastern Italy

2021 ◽  
Author(s):  
Peter Klin ◽  
Giovanna Laurenzano ◽  
Carla Barnaba ◽  
Enrico Priolo ◽  
Stefano Parolai
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Alluvial Soil ◽  
Site Amplification ◽  
Single Step ◽  
Reference Station ◽  
Ground Acceleration ◽  
Amplification Factors ◽  
Generalized Inversion ◽  
Northeastern Italy

ABSTRACT The application of earthquake recordings to the estimation of an event’s magnitude and the construction of rapid-response ground-motion maps requires an adequate classification of the recording stations in terms of their site response. For permanent stations, this information can be obtained from a sufficiently large database of past recordings. In this work, we analyze more than 7300 three-component recordings collected between 1996 and 2017 by 67 permanent stations in northeastern Italy to assess their site amplification. The signals come from 368 earthquakes with a magnitude range of M 3.2–5.8 and a distance range of 10–300 km. We evaluate the frequency-dependent amplification function with respect to a reference station with a flat seismic noise horizontal-to-vertical spectral ratio. The evaluation relies on the decomposition of the S-wave amplitude spectra in terms of source, propagation, and site response. We solve the decomposition with a nonparametric, single-step generalized inversion in the frequency band 0.5–20 Hz. In addition, we compute the amplification factors for peak ground acceleration and velocity with respect to a well-established ground-motion prediction equation. The results highlight that only 11 stations show a relatively flat unitary response with respect to the reference site, whereas the frequency-averaged amplification function at 23 out of 67 stations exhibits a value larger than 2. We classified the sites according to their surface geology and geomorphological scenario and found that amplification affects not only stations installed on the alluvial soil but also several stations installed on what are assumed to be rock sites. Sites in caves and mines exhibit deamplification, whereas the stations with sensors in boreholes exhibit the typical interference pattern. A good correlation between the amplification factors and the frequency-averaged amplification functions suggests the possibility of predicting time-domain peak ground-motion values from amplification functions estimated by generalized inversion.

A Quantitative Basis for Building Instrumentation Specifications

2011 ◽  
Vol 27 (1) ◽  
pp. 133-152 ◽  
Author(s):  
Derek A. Skolnik ◽  
Robert L. Nigbor ◽  
John W. Wallace
Keyword(s):  
Time Synchronization ◽  
Strong Motion ◽  
Sensitivity Analyses ◽  
Peak Ground Velocity ◽  
Ground Acceleration ◽  
Rate System ◽  
Intensity Measures ◽  
Quantitative Basis ◽  
Structural Responses ◽  
High Pass

A quantitative basis for key building instrumentation specifications—namely, sample rate, system resolution, and time synchronization—is established by quantifying the sensitivities of engineering demand parameters of peak floor acceleration and peak interstory drift to the errors associated with data acquisition. Details of the realistic simulation and digitization of structural responses are provided and automation of the seemingly signal-dependent procedure of high-pass digital filtering of relative displacements obtained by double numerical integration of accelerations is presented. Results from these studies, along with prior results from similar sensitivity analyses with respect to intensity measures of peak ground acceleration, peak ground velocity, and peak spectral acceleration, are used to recommend potential updates to structural instrumentation specifications of major strong-motion instrumentation programs.

scholarly journals New Ground Motion to Intensity Conversion Equations for China

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Xiufeng Tian ◽  
Zengping Wen ◽  
Weidong Zhang ◽  
Jie Yuan
Keyword(s):  
Ground Motion ◽  
Correction Term ◽  
Strong Motion ◽  
Seismic Intensity ◽  
Peak Ground Velocity ◽  
Ground Acceleration ◽  
Strong Earthquakes ◽  
Hypocentral Distance ◽  
Peak Ground Motion ◽  
Pseudo Spectral

In this study, we use the strong motion records and seismic intensity data from 11 moderate-to-strong earthquakes in the mainland of China since 2008 to develop new conversion equations between seismic intensity and peak ground motion parameters. Based on the analysis of the distribution of the dataset, the reversible conversion relationships between modified Mercalli intensity (MMI) and peak ground acceleration (PGA), peak ground velocity (PGV), and pseudo-spectral acceleration (PSA) at natural vibration periods of 0.3 s, 1.0 s, 2.0 s, and 3.0 s are obtained by using the orthogonal regression. The influence of moment magnitude, hypocentral distance, and hypocentral depth on the residuals of conversion equations is also explored. To account for and eliminate the trends in the residuals, we introduce a magnitude-distance-depth correction term and obtain the improved relationships. Furthermore, we compare the results of this study with previously published works and analyze the regional dependence of conversion equations. To quantify the regional variations, a regional correction factor for China, suitable for adjustment of global relationships, has also been estimated.

A Seismic Intensity Survey of the 16 April 2016 Mw 7.8 Pedernales, Ecuador, Earthquake: A Comparison with Strong-Motion Data and Teleseismic Backprojection

2021 ◽  
Author(s):  
Ellen M. Smith ◽  
Walter D. Mooney
Keyword(s):  
Emergency Response ◽  
Strong Motion ◽  
Seismic Intensity ◽  
Peak Ground Velocity ◽  
Ground Acceleration ◽  
Motion Data ◽  
Contour Maps ◽  
Crustal Earthquakes ◽  
Maximum Value ◽  
Large Earthquakes

Abstract We conducted a seismic intensity survey in Ecuador, following the 16 April 2016 Mw 7.8 Pedernales earthquake, to document the level of damage caused by the earthquake. Our modified Mercalli intensities (MMIs) reach a maximum value of VIII along the coast, where single, two, and multistory masonry and concrete designed buildings partially or completely collapsed. The contours of our MMI maps are similar in shape to the contour maps of peak ground acceleration (PGA) and peak ground velocity (PGV). A comparison of our seismic intensities with the recorded PGA and PGV values reveals that our MMI values are lower than predicted by ground-motion intensity conversion equations that are based on shallow crustal earthquakes. The image of the earthquake rupture obtained using teleseismic backprojection at 0.5–2.0 Hz is coincident with the region of maximum MMI, PGA, and PGV values, Thus, rapid calculation of backprojection may be a useful tool for guiding the deployment of emergency response teams following large earthquakes. The most severe damage observed was, primarily, due to a combination of poorly constructed buildings and site conditions.

Ground Motion from Mw 1.5 to 3.9 Aftershocks of the 2014 Mw 6.2 Jinggu Earthquake at Hypocentral Distances < 45 km in Yunnan, China

2019 ◽  
Author(s):  
Mengyao Sun ◽  
Huiyu Zhu ◽  
Jie Zhang ◽  
Haohuan Fu ◽  
Xiao Tian
Keyword(s):  
Ground Motion ◽  
Yunnan Province ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Prediction Equation ◽  
Peak Ground Velocity ◽  
Induced Earthquakes ◽  
Ground Acceleration ◽  
Hypocentral Distance ◽  
Fundamental Frequencies

ABSTRACT The ground motion from small aftershocks of the 2014 Mw 6.2 Jinggu earthquake in Yunnan Province is analyzed. With the seismic records, we assess the site conditions and develop a ground‐motion prediction equation (GMPE) for this region. The strong‐motion duration is also calculated to further understand the potential seismic hazard to nearby structures. The dataset includes 504 events with Mw 1.5–3.9 and 2956 three‐component records at hypocentral distances <45  km from 10 stations operated by the Earthquake Administration of Yunnan Province. The ground‐motion amplification factor derived from the horizontal‐to‐vertical (H/V) spectral ratio of each station ranges from 1.1 to 5.2 (0.04–0.72 in log units). The time‐averaged shear‐wave velocity to 30 m depth (VS30) for seismographic stations is estimated using fundamental frequencies associated with peak H/V ratios. GMPE is obtained using the entire dataset. The values of the geometrical spreading coefficient for the pseudoabsolute response spectral acceleration (PSA) at a frequency of 10 Hz suggest higher decay than those for the peak ground velocity, peak ground acceleration (PGA), and PSA at other frequencies. The significant duration (Ds) of strong ground motion systematically decreases with PGA but increases with hypocentral distance. However, no strong correlation is observed for Ds and magnitude or for Ds and VS30. The results of this study are compared with analogous research (Babaie Mahani and Kao, 2018) on induced earthquakes with the same distance–magnitude range. The comparison indicates that the decay of ground‐motion amplitudes with hypocentral distance in our case is generally lower than that in the other study. The Ds trends are consistent in the two studies, although the longest strong‐motion duration in the two cases apparently differs.

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