scholarly journals Variations of strong earthquake ground shaking in the Los Angeles area

1974 ◽  
Vol 64 (5) ◽  
pp. 1429-1454
Author(s):  
M. D. Trifunac ◽  
F. E. Udwadia
Keyword(s):  
Los Angeles ◽  
Ground Motion ◽  
Spectral Characteristics ◽  
Low Frequency ◽  
Soil Conditions ◽  
Minor Role ◽  
Ground Shaking ◽  
Local Soil ◽  
Recording Station ◽  
A Minor

Abstract Accelerograms recorded at six stations in the metropolitan Los Angeles area during the Borrego Mountain, 1968, the Lytle Creek, 1970, and the San Fernando, 1971, earthquakes in southern California have been studied. In comparing the ground motions recorded during different earthquakes at each of the six stations and in correlations of these motions recorded at different stations during the same earthquake, those aspects of the analysis which emerge from this study and are relevant for seismic zoning have been emphasized. It has been found that the patterns of strong ground shaking in this area depend predominantly on the mechanism and the distance of an earthquake source from a recording station and that the local soil conditions played only a minor role in modifying the ground motion at this particular area. It has been shown that gross spectral characteristics of ground motion recorded at various stations can be approximately related by the seismic moment at the low-frequency end and by the stress drop at the high-frequency end.

scholarly journals Investigating the influence of topographic irregularities and two-dimensional effects on surface ground motion intensity with one- and two-dimensional analyses

2014 ◽  
Vol 14 (7) ◽  
pp. 1773-1788 ◽  
Author(s):  
G. Ç. İnce ◽  
L. Yılmazoğlu
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Soil Conditions ◽  
Response Analysis ◽  
Two Dimensional ◽  
Ground Acceleration ◽  
Equivalent Linear ◽  
Local Soil ◽  
Different Depths ◽  
Earthquake Response Analysis

Abstract. In this work, the surface ground motion that occurs during an earthquake in ground sections having different topographic forms has been examined with one and two dynamic site response analyses. One-dimensional analyses were undertaken using the Equivalent-Linear Earthquake Response Analysis (EERA) program based on the equivalent linear analysis principle and the Deepsoil program which is able to make both equivalent linear and nonlinear analyses and two-dimensional analyses using the Plaxis 8.2 software. The viscous damping parameters used in the dynamic site response analyses undertaken with the Plaxis 8.2 software were obtained using the DeepSoil program. In the dynamic site response analyses, the synthetic acceleration over a 475-year return period representing the earthquakes in Istanbul was used as the basis of the bedrock ground motion. The peak ground acceleration obtained different depths of soils and acceleration spectrum values have been compared. The surface topography and layer boundaries in the 5-5' cross section which cuts across the study area west to east were selected in order to examine the effect of the land topography and layer boundaries on the analysis results, and were flattened and compared with the actual status. The analysis results showed that the characteristics of the surface ground motion change in relation to the varying local soil conditions and land topography.

scholarly journals Realistic modelling of observed seismic motion in compIex sedimentary basins

1994 ◽  
Vol 37 (6) ◽  
Author(s):  
D. Fah ◽  
G. F. Panza
Keyword(s):  
Ground Motion ◽  
Mexico City ◽  
Sedimentary Basin ◽  
Numerical Technique ◽  
Sedimentary Basins ◽  
Space Distribution ◽  
Soil Conditions ◽  
Macroseismic Data ◽  
Resonance Effects ◽  
Local Soil

Three applications of a numerical technique are illustrated to model realistically the seismic ground motion for complex two-dimensional structures. First we consider a sedimentary basin in the Friuli region, and we model strong motion records from an aftershock of the 1976 earthquake. Then we simulate the ground motion caused in Rome by the 1915, Fucino (Italy) earthquake, and we compare our modelling with the damage distribution observed in the town. Finally we deal with the interpretation of ground motion recorded in Mexico City, as a consequence of earthquakes in the Mexican subduction zone. The synthetic signals explain the major characteristics (relative amplitudes, spectral amplification, frequency content) of the considered seismograms, and the space distribution of the available macroseismic data. For the sedimentary basin in the Friuli area, parametric studies demonstrate the relevant sensitivity of the computed ground motion to small changes in the subsurface topography of the sedimentary basin, and in the velocity and quality factor of the sediments. The relative Arias Intensity, determined from our numerical simulation in Rome, is in very good agreoment with the distribution of damage observed during the Fucino earthquake. For epicentral distances in the range 50 km-100 km, the source location and not only the local soil conditions control the local effects. For Mexico City, the observed ground motion can be explained as resonance effects and as excitation of local surface waves, and the theoretical and the observed maximum spectral amplifications are very similar. In general, our numerical simulations estimate the maximum and average spectral amplification for specific sites, i.e. they are a very powerful tool for accurate micro-zonation

Evaluation of SCEC CyberShake Ground Motions for Engineering Practice

2019 ◽  
Vol 35 (3) ◽  
pp. 1311-1328 ◽  
Author(s):  
Ganyu Teng ◽  
Jack Baker
Keyword(s):  
Los Angeles ◽  
Ground Motion ◽  
Ground Motions ◽  
Response Spectra ◽  
Building Design ◽  
Empirical Models ◽  
Soil Conditions ◽  
Engineering Practice ◽  
Ground Motion Selection ◽  
Promising Source

This paper evaluates CyberShake (version 15.12) ground motions for potential application to high-rise building design in the Los Angeles region by comparing them against recordings from past earthquakes as well as empirical models. We consider two selected sites in the Los Angeles region with different underlying soil conditions and select comparable suites of ground motion records from CyberShake and the NGA-West2 database according to the ASCE 7-16 requirements. Major observations include (1) selected ground motions from CyberShake and NGA-West2 share similar features, in terms of response spectra and polarization; (2) when selecting records from Cyber-Shake, it is easy to select motions with sources that match the hazard deaggregation; (3) CyberShake durations on soil are consistent with the empirical models considered, whereas durations on rock are slightly shorter; (4) occasional excessive polarization in ground motion is produced by San Andreas fault ruptures, though those records are usually excluded after the ground motion selection. Results from this study suggest that CyberShake ground motions are a suitable and promising source of ground motions for engineering evaluations.

scholarly journals SEISMIC DAMAGE SCENARIOS IN KALAMATA (S. GREECE)

2017 ◽  
Vol 50 (3) ◽  
pp. 1495
Author(s):  
D. Kazantzidou-Firtinidou ◽  
I. Kassaras ◽  
A. Ganas ◽  
C. Tsimi ◽  
N. Sakellariou ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Fragility Curves ◽  
Site Amplification ◽  
Soil Conditions ◽  
Damage Scenarios ◽  
Local Soil ◽  
Protection Strategies ◽  
The Impact ◽  
The City

Damage scenarios are necessary tools for stakeholders, in order to prepare protection strategies and a total emergency post-earthquake plan. To this aim, four seismic hazard models were developed for the city of Kalamata, according to stochastic simulation of the ground motion, using site amplification functions derived from ambient noise HVSR measurements. The structural vulnerability of the city was assessed following an empirical macroseismic model, developed for the European urban environment (EMS-98). The impact of the vulnerability due to the seismic hazard potential is also investigated by means of synthetic response spectral ratios at 108 sites of the city. The expected damage grade per building block, is calculated by combining vulnerability with the respective seismic intensities, derived for the four seismic sources. The importance of the followed methodology for implementing microzonation studies is emphasized, since the expected influence of the ground motion amplification due to local soil conditions has been approximated in detail. Moreover, new fragility curves for the main structural types in Kalamata are proposed for each seismic scenario.

scholarly journals Towards preparation of design spectra for Serbian National Annex to Eurocode 8: Part I: spectral shapes and regional empirical equations for scaling pseudo-acceleration spectra

2012 ◽  
Vol 10 (2) ◽  
pp. 131-154
Author(s):  
Borko Bulajic ◽  
Miodrag Manic ◽  
Djordje Ladjinovic
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Strong Motion ◽  
Soil Conditions ◽  
Eurocode 8 ◽  
Empirical Equations ◽  
Strong Motion Data ◽  
Motion Data ◽  
Local Soil ◽  
Spectral Shapes

Eurocode 8 allows that any country can use its own shape of the elastic response spectrum after it defines it in the National Annex. Having in mind that such country-specific spectra are to be derived through analysis of the strong motion data recorded in the considered seismo-tectonic region, in this Paper we discuss the existing and a set of new empirical equations for scaling pseudo-acceleration spectra in Serbia and the whole region of north-western Balkans. We then compare the presented spectra to those proposed by Eurocode 8. Results show that the indiscriminate use of the strong motion data from different seismo-tectonic regions, improper classification of the local soil conditions, and neglect of the effects of deep geology, may all lead to unreliable scaling equations and to extremely biased ground motion estimates. Moreover, only two spectral shapes that are defined for wide magnitude ranges and scaled by a single PGA value, are not able to adequately represent all important features of real strong ground motion, and instead of using such normalized spectra one should rather employ the direct scaling of spectral amplitudes that is based on the analysis of regionally gathered and processed strong motion data.

scholarly journals Effects of finite source rupture on landslide triggering: The 2016 <i>M<sub>W</sub></i> 7.1 Kumamoto earthquake

2018 ◽  
Author(s):  
Sebastian von Specht ◽  
Ugur Ozturk ◽  
Georg Veh ◽  
Fabrice Cotton ◽  
Oliver Korup
Keyword(s):  
Radiation Pattern ◽  
Ground Motion ◽  
Low Frequency ◽  
New Physics ◽  
Rupture Directivity ◽  
Ground Shaking ◽  
Kumamoto Earthquake ◽  
Directivity Effect ◽  
Seismic Rupture ◽  
Landslide Distribution

Abstract. The propagation of a seismic rupture on a fault introduces spatial variations in the seismic wavefield surrounding the fault during an earthquake. This directivity effect results in larger shaking amplitudes in the rupture propagation direction. Its seismic radiation pattern also causes amplitude variations between the strike-normal and strike-parallel components of horizontal ground motion. We investigated the landslide response to these effects during the 2016 Kumamoto earthquake (MW 7.1) in central Kyūshū (Japan). Although the distribution of some 1,500 earthquake-triggered landslides as function of rupture distance is consistent with the observed Arias intensity, the landslides are more concentrated to the northeast of the southwest-northeast striking rupture. We examined several landslide susceptibility factors: hillslope inclination, median amplification factor (MAF) of ground shaking, lithology, land cover, and topographic wetness. None of these factors can sufficiently explain the landslide distribution or orientation (aspect), although the landslide headscarps coincide with elevated hillslope inclination and MAF. We propose a new physics-based ground motion model that accounts for the seismic rupture effects, and demonstrate that the low-frequency seismic radiation pattern consistent with the overall landslide distribution. The spatial landslide distribution is primarily influenced by the rupture directivity effect, whereas landslide aspect is influenced by amplitude variations between the fault-normal and fault-parallel motion at frequencies

On: “Ionospheric induced very low frequency electric field wavetilt changes” by D. V. Thiel and I. J. Chant (GEOPHYSICS, Jan., 1982, p. 60–62)

Geophysics ◽  
1984 ◽  
Vol 49 (8) ◽  
pp. 1388-1388
Author(s):  
James R. Wait
Keyword(s):  
Electric Field ◽  
Surface Impedance ◽  
Low Frequency ◽  
Impedance Measurement ◽  
Minor Role ◽  
Elliptical Polarization ◽  
Vertical Electric Field ◽  
A Minor ◽  
Ground Wave ◽  
Measuring Scheme

With all due respect to Singh and Rankin (1983), I believe that their criticism of the paper by Thiel and Chant (cited above) needs clarification. Contrary to the assertion by Singh and Rankin, the quoted formula for the function [Formula: see text] (incorrectly called a wavetilt) can indeed depend upon the mode of propagation. The factor sin θ, appearing in the quoted expressions, is the sine of the complex angle of the incident wave whether it be a ground wave or a downgoing ionospherically reflected wave. This point is central to the long‐standing dispute between the “Cagniard school” of magnetotelluric sounding and those who believe that source field characteristics can play a role. Thiel and Chant correctly pointed out that the elliptical polarization of the downgoing wave can mess up the results. But possibly they overlooked that this effect, in a surface impedance measurement, is minimized compared with a true wavetilt measurement. The latter senses the vertical electric field with a vertical (i.e., whip) antenna, whereas in a true surface impedance measuring scheme both horizontal E and horizontal H fields are sensed. Actually Thiel and Chant measured surface impedance, so the elliptical polarization of the downgoing wave probably plays a minor role.

scholarly journals A Quantitative Approach to Assess Seismic Vulnerability of Touristic Accommodations: Case Study in Montreal, Canada

GeoHazards ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 137-152
Author(s):  
Thomas Candela ◽  
Philippe Rosset ◽  
Luc Chouinard
Keyword(s):  
Seismic Vulnerability ◽  
Significant Proportion ◽  
Vulnerability Index ◽  
Soil Conditions ◽  
Building Vulnerability ◽  
Ground Shaking ◽  
Rapid Visual Screening ◽  
Local Soil ◽  
Four Levels

In many places of the world, the interruption of touristic activities in the aftermath of a catastrophic earthquake is often neglected in the evaluation of seismic risks; however, these activities can account for a significant proportion of short-term and long-term economic impacts for these regions. In the last decade, several rapid visual screening techniques have been developed to define the typology of buildings and to estimate their seismic vulnerability and potential for damage. We adapted the existing screening procedures that have been developed for generic buildings to specific circumstances that are most common for tourist accommodations. The proposed approach considered six criteria related to structural and nonstructural elements of buildings, as well as local soil conditions. A score was assigned to each criterion as a function of the capacity of the elements to resist ground shaking. A vulnerability index in four levels of building vulnerability was developed combining the scores of the six criteria. The approach was tested in a pilot area of Montreal to a set of 70 typical buildings grouped in four categories based on their accommodation capacity. In Montreal, tourism is an important source of income for the city where 351,000 room-nights were booked with total stay expenditures of CAD 4.9 billion in 2019. The results indicated potential significant disruptions in activities related to tourism; 46% of the buildings investigated have a high to very high vulnerability index. Among them, 4/5 are located in the old city and 1/5 in the downtown area of the pilot zone.

scholarly journals Effects of finite source rupture on landslide triggering: the 2016 <i>M</i><sub>w</sub> 7.1 Kumamoto earthquake

Solid Earth ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 463-486 ◽  
Author(s):  
Sebastian von Specht ◽  
Ugur Ozturk ◽  
Georg Veh ◽  
Fabrice Cotton ◽  
Oliver Korup
Keyword(s):  
Radiation Pattern ◽  
Ground Motion ◽  
Low Frequency ◽  
New Physics ◽  
Rupture Directivity ◽  
Ground Shaking ◽  
Kumamoto Earthquake ◽  
Directivity Effect ◽  
Seismic Rupture ◽  
Landslide Distribution

Abstract. The propagation of a seismic rupture on a fault introduces spatial variations in the seismic wave field surrounding the fault. This directivity effect results in larger shaking amplitudes in the rupture propagation direction. Its seismic radiation pattern also causes amplitude variations between the strike-normal and strike-parallel components of horizontal ground motion. We investigated the landslide response to these effects during the 2016 Kumamoto earthquake (Mw 7.1) in central Kyushu (Japan). Although the distribution of some 1500 earthquake-triggered landslides as a function of rupture distance is consistent with the observed Arias intensity, the landslides were more concentrated to the northeast of the southwest–northeast striking rupture. We examined several landslide susceptibility factors: hillslope inclination, the median amplification factor (MAF) of ground shaking, lithology, land cover, and topographic wetness. None of these factors sufficiently explains the landslide distribution or orientation (aspect), although the landslide head scarps have an elevated hillslope inclination and MAF. We propose a new physics-based ground-motion model (GMM) that accounts for the seismic rupture effects, and we demonstrate that the low-frequency seismic radiation pattern is consistent with the overall landslide distribution. Its spatial pattern is influenced by the rupture directivity effect, whereas landslide aspect is influenced by amplitude variations between the fault-normal and fault-parallel motion at frequencies <2 Hz. This azimuth dependence implies that comparable landslide concentrations can occur at different distances from the rupture. This quantitative link between the prevalent landslide aspect and the low-frequency seismic radiation pattern can improve coseismic landslide hazard assessment.

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