Istanbul at the Threshold: An Evaluation of the Seismic Risk in Istanbul

2007 ◽  
Vol 23 (1) ◽  
pp. 63-75 ◽  
Author(s):  
Jacob H. Pyper Griffiths ◽  
Ayhan Irfanoglu ◽  
Santiago Pujol
Keyword(s):  
Ground Motion ◽  
Emergency Response ◽  
Seismic Risk ◽  
Ground Motions ◽  
Convincing Evidence ◽  
Severe Damage ◽  
Future Earthquake ◽  
The City ◽  
Better Than

There is no convincing evidence indicating that future ground motion in at least two-thirds of Istanbul, Turkey, shall be less demanding than the ground motions that devastated the city of Düzce, Turkey, in 1999. Comparison of vulnerability indices calibrated for Turkish construction indicates that the structures of the buildings in Istanbul are no better than the structures of buildings in Düzce. On the basis of these arguments, we project that a future earthquake near Istanbul may cause severe damage or collapse approximately quarter of a million buildings. Leaving the vulnerable buildings as they are and organizing for emergency response is not an option for Istanbul.

Contribution for seismic hazard assessment with local scale focus on Durrës (Albania) and damage observation after the ML 5.4, 21st September 2019 earthquake

2020 ◽  
Author(s):  
Marco Mancini ◽  
Iolanda Gaudiosi ◽  
Redi Muci ◽  
Maurizio Simionato ◽  
Klodian Skrame
Keyword(s):  
Seismic Hazard ◽  
Cultural Heritage ◽  
Ground Motion ◽  
Seismic Risk ◽  
Preliminary Results ◽  
Joint Research Project ◽  
Single Station ◽  
Noise Measurements ◽  
The City ◽  
2D Array

<p>The city of Durrës was recentely struck by a Mw 6.2 mainshock event (http://cnt.rm.ingv.it/event/23487611) that caused considerable damage and 51 victims. The city is located on an actively seismotectonic belt where seismic catalogues report few past events with magnitude higher than 6.</p><p>Surface geology is generally considered to influence the ground motion recorded on site. The analysis of the influence of local effects on seismic response at ground surface appears relevant also considering that Durrës is a densely populated city prone to high seismic risk and is characterized by several important archeological and cultural heritage sites.</p><p>Preliminary results obtained from recent geophysical in-situ measurements and geological surveys, carried out in Durrës after the ML 5.4, 21<sup>st</sup> September 2019 event, are presented with the aim of providing new elements for the assessment of local seismic hazard and following a comprehensive approach to the modifications induced by the site.</p><p>Twenty-nine single-station noise measurements, processed through the HVSR technique, two MASW surveys and two 2D array measurements were performed. Results from noise measurements define a zone eastward of the historical centre, where the characteristics of surficial soil layers are responsible for modification to the seismic demand. In particular, HVSR curves in this area show amplification higher than 4 at a period higher than 1s. Moreover, on this location a surface waves-velocity profile obtained from a joint inversion of Rayleigh curves from MASW and 2D array with ellipticity individuates a class D soil, EC8 sensu, corresponding to marshy soil of very poor geotechnical quality. These data may be considered as key elements in the site-specific response analyses, i.e. realized according to the international codes (EC8, NEHRP), which allow to quantify the expected ground motion. These results are potentially useful for  correlating  construction typologies and period vibration of the buildings with the site amplification.</p><p>In addition, a damage survey was carried out in one of the most damaged zones after the 21<sup>st</sup> September 2019 earthquake. Because of the following stronger event of the 26<sup>th</sup> November 2019, we think that these preliminary results may provide useful information for the post-earthquake reconstruction and enhancement of the urban resilience.</p><p>                The activities are carried out wihin the framework of the CNR/MOES Joint research project “Seismic risk assessment in cultural heritage cities of Albania” in the biennium 2018-2019 (https://www.cnr.it/en/bilateral-agreements/agreement/60/moes-ministry-of-education-and-sport-of-the-republic-of-albania).</p>

scholarly journals Hazard-consistent seismic losses and collapse capacities for light-frame wood buildings in California and Cascadia

2021 ◽  
Author(s):  
Robert E. Chase ◽  
Abbie B. Liel ◽  
Nicolas Luco ◽  
Zach Bullock
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Seismic Risk ◽  
Ground Motions ◽  
Spectral Shape ◽  
Economic Losses ◽  
Frequency Content ◽  
Crustal Earthquakes ◽  
Design Values ◽  
American Society

AbstractWe evaluate the seismic performance of modern seismically designed wood light-frame (WLF) buildings, considering regional seismic hazard characteristics that influence ground motion duration and frequency content and, thus, seismic risk. Results show that WLF building response correlates strongly with ground motion spectral shape but weakly with duration. Due to the flatter spectral shape of ground motions from subduction events, WLF buildings at sites affected by these earthquakes may experience double the economic losses for a given intensity of shaking, and collapse capacities may be reduced by up to 50%, compared to those at sites affected by crustal earthquakes. These differences could motivate significant increases in design values at sites affected by subduction earthquakes to achieve the uniform risk targets of the American Society of Civil Engineers (ASCE) 7 standard.

scholarly journals Nonlinear Deterministic Study of Seismic Microzoning of a City in North of Algeria

2019 ◽  
Vol 5 (8) ◽  
pp. 1774-1787 ◽  
Author(s):  
Badreddine Bousbia ◽  
Badreddine Sbartai
Keyword(s):  
Seismic Risk ◽  
Ground Motions ◽  
Response Spectra ◽  
Seismic Microzonation ◽  
Ground Movement ◽  
Geological Model ◽  
Ground Acceleration ◽  
History Of ◽  
The City ◽  
Boumerdes Earthquake

This paper presents also an overview of seismic microzonation studies of the city of Mohammadia-Algiers, which are important for a detailed ground movement modeling of urban cities. According to the seismic history of the city, one extraordinary earthquake event has been taken into consideration is Boumerdes earthquake (Algeria, May 21, 2003, magnitude Mw=6.5), that caused a huge damage. Thereby, the variability prediction of the seismic ground movement in a given built-up area, it is considered as an effective tool for planning appropriate urban development and understanding both seismic risk and damage pattern, caused by a strong movement event. We note that the shaking level is mainly described in terms of both maximum ground acceleration and visualized amplification by using response spectra. The study is carried out in two steps: - a detailed mapping of the geology and geotechnical properties of the area - numerical modeling of expected ground motions during earthquakes. A qualitative microzonation of the Mohammadia-Algiers city is presented, and it is discussed by comparing it to the historically reported damage of the 2003 Boumerdes earthquake. Finally, this study deals with the seismic microzonation map development, based on a SIG geological model.

Which Spectral Acceleration are you Using?

2006 ◽  
Vol 22 (2) ◽  
pp. 293-312 ◽  
Author(s):  
Jack W. Baker ◽  
C. Allin Cornell
Keyword(s):  
Seismic Risk ◽  
Hazard Analysis ◽  
Ground Motions ◽  
Geometric Mean ◽  
Response Analysis ◽  
Spectral Acceleration ◽  
Intensity Measure ◽  
Structure Response ◽  
Future Earthquake ◽  
Structural Engineers

Analysis of the seismic risk to a structure requires assessment of both the rate of occurrence of future earthquake ground motions (hazard) and the effect of these ground motions on the structure (response). These two pieces are often linked using an intensity measure such as spectral acceleration. However, earth scientists typically use the geometric mean of the spectral accelerations of the two horizontal components of ground motion as the intensity measure for hazard analysis, while structural engineers often use spectral acceleration of a single horizontal component as the intensity measure for response analysis. This inconsistency in definitions is typically not recognized when the two assessments are combined, resulting in unconservative conclusions about the seismic risk to the structure. The source and impact of the problem is examined in this paper, and several potential resolutions are proposed. This discussion is directly applicable to probabilistic analyses, but also has implications for deterministic seismic evaluations.

scholarly journals TriNet “ShakeMaps”: Rapid Generation of Peak Ground Motion and Intensity Maps for Earthquakes in Southern California

1999 ◽  
Vol 15 (3) ◽  
pp. 537-555 ◽  
Author(s):  
David J. Wald ◽  
Vincent Quitoriano ◽  
Thomas H. Heaton ◽  
Hiroo Kanamori ◽  
Craig W. Scrivner ◽  
...  
Keyword(s):  
Ground Motion ◽  
Emergency Response ◽  
Spatial Interpolation ◽  
Southern California ◽  
Ground Motions ◽  
Peak Ground Motion ◽  
The World ◽  
Motion Parameters ◽  
Dependent Site ◽  
Rapid Generation

Rapid (3-5 minutes) generation of maps of instrumental ground-motion and shaking intensity is accomplished through advances in real-time seismographic data acquisition combined with newly developed relationships between recorded ground-motion parameters and expected shaking intensity values. Estimation of shaking over the entire regional extent of southern California is obtained by the spatial interpolation of the measured ground motions with geologically based frequency and amplitude-dependent site corrections. Production of the maps is automatic, triggered by any significant earthquake in southern California. Maps are now made available within several minutes of the earthquake for public and scientific consumption via the World Wide Web; they will be made available with dedicated communications for emergency response agencies and critical users.

A subset of CyberShake ground-motion time series for response-history analysis

2021 ◽  
pp. 875529302098197
Author(s):  
Jack W Baker ◽  
Sanaz Rezaeian ◽  
Christine A Goulet ◽  
Nicolas Luco ◽  
Ganyu Teng
Keyword(s):  
Time Series ◽  
Los Angeles ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Ground Motions ◽  
Response Spectra ◽  
Motion Time ◽  
History Analysis ◽  
Response History Analysis ◽  
Simulated Ground Motions

This manuscript describes a subset of CyberShake numerically simulated ground motions that were selected and vetted for use in engineering response-history analyses. Ground motions were selected that have seismological properties and response spectra representative of conditions in the Los Angeles area, based on disaggregation of seismic hazard. Ground motions were selected from millions of available time series and were reviewed to confirm their suitability for response-history analysis. The processes used to select the time series, the characteristics of the resulting data, and the provided documentation are described in this article. The resulting data and documentation are available electronically.

Ground-motion model for subduction earthquakes in northern South America

2021 ◽  
pp. 875529302110275
Author(s):  
Carlos A Arteta ◽  
Cesar A Pajaro ◽  
Vicente Mercado ◽  
Julián Montejo ◽  
Mónica Arcila ◽  
...  
Keyword(s):  
South America ◽  
Ground Motion ◽  
Ground Motions ◽  
Strong Motion ◽  
Motion Prediction ◽  
Depth Range ◽  
Ground Motion Prediction ◽  
Natural Period ◽  
Nazca Plate ◽  
Northern South America

Subduction ground motions in northern South America are about a factor of 2 smaller than the ground motions for similar events in other regions. Nevertheless, historical and recent large-interface and intermediate-depth slab earthquakes of moment magnitudes Mw = 7.8 (Ecuador, 2016) and 7.2 (Colombia, 2012) evidenced the vast potential damage that vulnerable populations close to earthquake epicenters could experience. This article proposes a new empirical ground-motion prediction model for subduction events in northern South America, a regionalization of the global AG2020 ground-motion prediction equations. An updated ground-motion database curated by the Colombian Geological Survey is employed. It comprises recordings from earthquakes associated with the subduction of the Nazca plate gathered by the National Strong Motion Network in Colombia and by the Institute of Geophysics at Escuela Politécnica Nacional in Ecuador. The regional terms of our model are estimated with 539 records from 60 subduction events in Colombia and Ecuador with epicenters in the range of −0.6° to 7.6°N and 75.5° to 79.6°W, with Mw≥4.5, hypocentral depth range of 4 ≤  Zhypo ≤ 210 km, for distances up to 350 km. The model includes forearc and backarc terms to account for larger attenuation at backarc sites for slab events and site categorization based on natural period. The proposed model corrects the median AG2020 global model to better account for the larger attenuation of local ground motions and includes a partially non-ergodic variance model.

scholarly journals Vertical to Horizontal UHS Ratios for Low to Medium Seismicity Regions with Deep Soil atop Deep Geological Sediments—An Example of the City of Osijek, Croatia

2021 ◽  
Vol 11 (15) ◽  
pp. 6782
Author(s):  
Borko Đ. Bulajić ◽  
Marijana Hadzima-Nyarko ◽  
Gordana Pavić
Keyword(s):  
Ground Motions ◽  
Spectral Amplitude ◽  
Eurocode 8 ◽  
Uniform Hazard Spectra ◽  
Study Region ◽  
Spectral Estimates ◽  
Local Soil ◽  
The Impact ◽  
Deep Soils ◽  
The City

The severity of vertical seismic ground motions is often factored into design regulations as a component of their horizontal counterparts. Furthermore, most design codes, including Eurocode 8, ignore the impact of local soil on vertical spectra. This paper investigates vertical pseudo-absolute acceleration spectral estimates, as well as the ratios of spectral estimates for strong motion in vertical and horizontal directions, for low to medium seismicity regions with deep local soil and deep geological sediments beneath the local soil. The case study region encompasses the city of Osijek in Croatia. New regional frequency-dependent empirical scaling equations are derived for the vertical spectra. According to these equations, for a 0.3 s spectral amplitude at deep soils atop deep geological sediments compared to the rock sites, the maximum amplification is 1.48 times. The spectra of vertical components of various real strong motions recorded in the surrounding region are compared to the empirical vertical response spectra. The new empirical equations are used to construct a Uniform Hazard Spectra for Osijek. The ratios of vertical to horizontal Uniform Hazard Spectra are generated, examined, and compared to Eurocode 8 recommendations. All the results show that local soil and deep geology conditions have a significant impact on vertical ground motions. The results also show that for deep soils atop deep geological strata, Eurocode 8 can underestimate the vertical to horizontal spectral ratios by a factor of three for Type 2 spectra while overestimating them by a factor of two for Type 1 spectra.

Site effects of the Denis-Perron dam (SM-3): A case study in Eastern North America

2021 ◽  
pp. 875529302110194
Author(s):  
Daniel Verret ◽  
Denis LeBœuf ◽  
Éric Péloquin
Keyword(s):  
North America ◽  
Ground Motion ◽  
Site Effects ◽  
Transfer Functions ◽  
Ground Motions ◽  
Published Data ◽  
Eastern North America ◽  
Ground Acceleration ◽  
Large Dams ◽  
Moderate Seismicity

Eastern North America (ENA) is part of a region with low-to-moderate seismicity; nonetheless, some significant seismic events have occurred in the last few decades. Recent events have reemphasized the need to review ENA seismicity and ground motion models, along with continually reevaluating and updating procedures related to the seismic safety assessment of hydroelectric infrastructures, particularly large dams in Québec. Furthermore, recent researchers have shown that site-specific characteristics, topography, and valley shapes may significantly aggravate the severity of ground motions. To the best of our knowledge, very few instrumental data from actual earthquakes have been published for examining the site effects of hydroelectric dam structures located in eastern Canada. This article presents an analysis of three small earthquakes that occurred in 1999 and 2002 at the Denis-Perron (SM-3) dam. This dam, the highest in Québec, is a rockfill embankment structure with a height of 171 m and a length of 378 m; it is located in a narrow valley. The ground motion datasets of these earthquakes include the bedrock and dam crest three-component accelerometer recordings. Ground motions are analyzed both in the time and frequency domains. The spectral ratios and transfer functions obtained from these small earthquakes provide new insights into the directionality of resonant frequencies, vibration modes, and site effects for the Denis-Perron dam. The crest amplifications observed for this dam are also compared with previously published data for large dams. New statistical relationships are proposed to establish dam crest amplification on the basis of the peak ground acceleration (PGA) at the foundation.

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