Stability of earthquake ground motion synthesized by using different small-event records as empirical Green's functions

1990 ◽  
Vol 80 (6A) ◽  
pp. 1433-1455 ◽  
Author(s):  
K. Dan ◽  
T. Watanabe ◽  
T. Tanaka ◽  
R. Sato
Keyword(s):  
Ground Motion ◽  
Green's Functions ◽  
Green’S Functions ◽  
Ground Motions ◽  
Source Parameters ◽  
Earthquake Ground Motion ◽  
Source Spectrum ◽  
Similarity Relations ◽  
Coefficients Of Variation ◽  
Synthesis Procedure

Abstract The semi-empirical method, in which small-event records are used as Green's functions to synthesize strong ground motions from a large earthquake, has become one of the most practical methods for generating the input ground motion for earthquake-resistant design of structures. The stability of the synthesized ground motions was examined in the applicability for engineering purposes. The accelerograms from the 1980 Izu-Hanto-Toho-Oki, Japan, earthquake with a magnitude of 6.7 were simulated by using the records from 17 foreshocks and aftershocks with magnitudes of 3.4 to 4.9. The syntheses were carried out for each small-event record and 17 results are obtained. The coefficients of variation (percentages of the standard deviations to the mean values) of the ratios of the synthesized PGA, PGV and SI to the observed ones were found to be 40 to 80 per cent, which consisted of 20 to 30 per cent caused by our synthesis procedure itself, 30 to 40 per cent caused by the approximation of the source spectrum for each small event by the ω-square model, and 0 to 70 per cent caused by the similarity relations used to obtain the source parameters (L, W, D, and σe from the magnitude. Consequently, in order to minimize the variation caused by the modeling of the source spectrum and the similarity relations, we proposed a new synthesis procedure, in which the small-event records were normalized with regard to the source size and then chosen randomly as Green's functions for each element of the fault plane of the main shock. The coefficients of variation of the results by the present new procedure became 15 to 25 per cent much more stable.

An Earthquake Source Spectrum Model Considering Rupture Directivity and Its Application for Obtaining Green’s Functions

2020 ◽  
Vol 110 (6) ◽  
pp. 2711-2727
Author(s):  
Shota Shimmoto
Keyword(s):  
Ground Motion ◽  
Green's Functions ◽  
Green’S Functions ◽  
Ground Motions ◽  
Source Spectrum ◽  
Rupture Directivity ◽  
Small Earthquake ◽  
Finite Fault ◽  
Ground Motion Records ◽  
Spectrum Model

ABSTRACT A small earthquake with strong rupture directivity is inappropriate to use as a point source when estimating ground motion. A source spectrum model is proposed to remove the effects of rupture directivity and finite fault size from observed earthquakes. This model is developed by using a kinematic source model of a rectangular fault with bilateral-bidirectional rupture propagation. Its amplitude spectrum is modeled to decay as ω−2 at high frequency and is approximated by its envelope to make deconvolution a stable operation. The effectiveness of the proposed spectrum model is demonstrated through application to the two aftershocks of Mw 4.0 and Mw 5.5 observed following the 2016 Kumamoto earthquake. These aftershocks had similar focal mechanisms and were located near to each other. A method to estimate the source parameters by using the proposed spectrum model is presented and its effectiveness is demonstrated. The deconvolution of the ground-motion records using a suitable source spectrum model gives us the Green’s function. The amplitude spectra of the Green’s functions obtained from both observed aftershock events are shown to be consistent. The far-field ground motions are simulated by using the Green’s functions. The simulated ground motions match well with the observed ones. Simulation of the ground motions by using the Green’s functions obtained from the deconvolution of ground-motion records by the proposed spectrum model has an advantage compared to the use of small earthquake records as empirical Green’s functions (EGFs). Specifically, this approach reduces the variation in ground-motion simulation results due to the choice of different EGFs.

scholarly journals A technique for simulating strong ground motion using hybrid Green's function

1998 ◽  
Vol 88 (2) ◽  
pp. 357-367 ◽  
Author(s):  
Katsuhiro Kamae ◽  
Kojiro Irikura ◽  
Arben Pitarka
Keyword(s):  
Green’S Function ◽  
Ground Motion ◽  
Green's Function ◽  
Green's Functions ◽  
Strong Ground Motion ◽  
Green’S Functions ◽  
Ground Motions ◽  
Large Earthquake ◽  
Long Period ◽  
Strong Ground

Abstract A method for simulating strong ground motion for a large earthquake based on synthetic Green's function is presented. We use the synthetic motions of a small event as Green's functions instead of observed records of small events. Ground motions from small events are calculated using a hybrid scheme combining deterministic and stochastic approaches. The long-period motions from the small events are deterministically calculated using the 3D finite-difference method, whereas the high-frequency motions from them are stochastically simulated using Boore's method. The small-event motions are synthesized summing the long-period and short-period motions after passing them through a pair of matched filters to follow the omega-squared source model. We call the resultant time series “hybrid Green's functions” (HGF). Ground motions from a large earthquake are simulated by following the empirical Green's function (EGF) method. We demonstrate the effectiveness of the method at simulating ground motion from the 1995 Hyogo-ken Nanbu earthquake (Mw 6.9).

A Monte Carlo approach to seismic hazard analysis

1999 ◽  
Vol 89 (4) ◽  
pp. 854-866 ◽  
Author(s):  
John E. Ebel ◽  
Alan L. Kafka
Keyword(s):  
Monte Carlo ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Epicentral Distance ◽  
Ground Motions ◽  
Source Parameters ◽  
Parametric Models ◽  
Earthquake Catalog ◽  
Attenuation Relations ◽  
Ground Motion Attenuation

Abstract We have developed a Monte Carlo methodology for the estimation of seismic hazard at a site or across an area. This method uses a multitudinous resampling of an earthquake catalog, perhaps supplemented by parametric models, to construct synthetic earthquake catalogs and then to find earthquake ground motions from which the hazard values are found. Large earthquakes extrapolated from a Gutenberg-Richter recurrence relation and characteristic earthquakes can be included in the analysis. For the ground motion attenuation with distance, the method can use either a set of observed ground motion observations from which estimates are randomly selected, a table of ground motion values as a function of epicentral distance and magnitude, or a parametric ground motion attenuation relation. The method has been tested for sites in New England using an earthquake catalog for the northeastern United States and southeastern Canada, and it yields reasonable ground motions at standard seismic hazard values. This is true both when published ground motion attenuation relations and when a dataset of observed peak acceleration observations are used to compute the ground motion attenuation with distance. The hazard values depend to some extent on the duration of the synthetic catalog and the specific ground motion attenuation used, and the uncertainty in the ground motions increases with decreasing hazard probability. The program gives peak accelerations that are comparable to those of the 1996 U.S. national seismic hazard maps. The method can be adapted to compute seismic hazard for cases where there are temporal or spatial variations in earthquake occurrence rates or source parameters.

Evaluation of Earthquake Response Spectra Directionality Using Stochastic Simulations

2021 ◽  
Author(s):  
Alan Poulos ◽  
Eduardo Miranda ◽  
Jack W. Baker
Keyword(s):  
Stochastic Process ◽  
Ground Motion ◽  
Ground Motions ◽  
Gaussian White Noise ◽  
Response Spectra ◽  
Orientation Dependence ◽  
Stochastic Simulations ◽  
Earthquake Ground Motion ◽  
Significant Duration ◽  
Simulated Ground Motions

ABSTRACT For earthquake-resistant design purposes, ground-motion intensity is usually characterized using response spectra. The amplitude of response spectral ordinates of horizontal components varies significantly with changes in orientation. This change in intensity with orientation is commonly known as ground-motion directionality. Although this directionality has been attributed to several factors, such as topographic irregularities, near-fault effects, and local geologic heterogeneities, the mechanism behind this phenomenon is still not well understood. This work studies the directionality characteristics of earthquake ground-motion intensity using synthetic ground motions and compares their directionality to that of recorded ground motions. The two principal components of horizontal acceleration are sampled independently using a stochastic model based on finite-duration time-modulated filtered Gaussian white-noise processes. By using the same stochastic process to sample both horizontal components of motion, the variance of horizontal ground acceleration has negligible orientation dependence. However, these simulations’ response spectral ordinates present directionality levels comparable to those found in real ground motions. It is shown that the directionality of the simulated ground motions changes for each realization of the stochastic process and is a consequence of the duration being finite. Simulated ground motions also present similar directionality trends to recorded earthquake ground motions, such as the increase of average directionality with increasing period of vibration and decrease with increasing significant duration. These results suggest that most of the orientation dependence of horizontal response spectra is primarily explained by the finite significant duration of earthquake ground motion causing inherent randomness in response spectra, rather than by some physical mechanism causing polarization of shaking.

Rupture Process of the Mainshock of the 2019 Ridgecrest Earthquake Sequence from Waveform Inversion with Empirical Green’s Functions

2021 ◽  
Author(s):  
Shuang-Lan Wu ◽  
Atsushi Nozu ◽  
Yosuke Nagasaka
Keyword(s):  
Green's Functions ◽  
Green’S Functions ◽  
Ground Motions ◽  
Strong Motion ◽  
Rupture Process ◽  
Earthquake Sequence ◽  
Slip Model ◽  
Near Fault ◽  
Empirical Green’S Functions ◽  
Empirical Green's Functions

ABSTRACT The 2019 Mw 7.1 mainshock of the Ridgecrest earthquake sequence, which was the first event exceeding Mw 7.0 in California since the 1999 Hector Mine earthquake, caused near-fault ground motions exceeding 0.5g and 70  cm/s. In this study, the rupture process and the generation mechanism of strong ground motions of the mainshock were investigated through waveform inversions of strong-motion data in the frequency range of 0.2–2.0 Hz using empirical Green’s functions (EGFs). The results suggest that the mainshock involved two large slip regions: the primary one with a maximum slip of approximately 4.4 m was centered ∼3  km northwest of the hypocenter, which was slightly shallower than the hypocenter, and the secondary one was centered ∼25  km southeast of the hypocenter. Outside these regions, the slip was rather small and restricted to deeper parts of the fault. A relatively small rupture velocity of 2.1  km/s was identified. The robustness of the slip model was examined by conducting additional inversion analyses with different combinations of EGF events and near-fault stations. In addition, using the preferred slip model, we synthesized strong motions at stations that were not used in the inversion analyses. The synthetic waveforms captured the timing of the main phases of observed waveforms, indicating the validity of the major spatiotemporal characteristics of the slip model. Our large slip regions are also generally visible in the models proposed by other researchers based on different datasets and focusing on lower frequency ranges (generally lower than 0.5 Hz). In particular, two large slip regions in our model are very consistent with two of the four subevents identified by Ross et al. (2019), which may indicate that part of the large slip regions that generated low-frequency ground motions also generated high-frequency ground motions up to 2.0 Hz during the Ridgecrest mainshock.

SEISMIC COLLAPSING ANALYSIS OF ONE-STORY WOODEN KINDERGARTEN STRUCTURE AGAINST STRONG EARTHQUAKE GROUND MOTION

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Tomiya Takatani ◽  
Hayato Nishikawa
Keyword(s):  
Ground Motion ◽  
Strong Earthquake ◽  
Process Analysis ◽  
Ground Motions ◽  
Seismic Intensity ◽  
Earthquake Ground Motion ◽  
Intensity Level ◽  
Wooden Structure ◽  
Old Japanese ◽  
Upper Level

3-D collapsing process analysis of an old Japanese-style one-story wooden structure under two strong earthquake ground motions with a seismic intensity level was car-ried out in order to investigate the seismic performance of this one-story wooden structure without/with seismic retrofit. As a result, this wooden structure collapsed against a strong earthquake ground motion with the JMA seismic intensity “6 upper” level.

STOCHASTIC SEISMIC RESPONSE OF BASE-ISOLATED BUILDINGS

2013 ◽  
Vol 05 (01) ◽  
pp. 1350006 ◽  
Author(s):  
C. JACOB ◽  
K. SEPAHVAND ◽  
V. A. MATSAGAR ◽  
S. MARBURG
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Probability Distributions ◽  
Ground Motions ◽  
Earthquake Ground Motion ◽  
Response Analysis ◽  
Motion Model ◽  
Stochastic Response ◽  
Ground Motion Model ◽  
Stochastic Seismic Response

The stochastic response of base-isolated building considering the uncertainty in the characteristics of the earthquakes is investigated. For this purpose, a probabilistic ground motion model, for generating artificial earthquakes is developed. The model is based upon a stochastic ground motion model which has separable amplitude and spectral non-stationarities. An extensive database of recorded earthquake ground motions is created. The set of parameters required by the stochastic ground motion model to depict a particular ground motion is evaluated for all the ground motions in the database. Probability distributions are created for all the parameters. Using Monte Carlo (MC) simulations, the set of parameters required by the stochastic ground motion model to simulate ground motions is obtained from the distributions and ground motions. Further, the bilinear model of the isolator described by its characteristic strength, post-yield stiffness and yield displacement is used, and the stochastic response is determined by using an ensemble of generated earthquakes. A parametric study is conducted for the various characteristics of the isolator. This study presents an approach for stochastic seismic response analysis of base-isolated building considering the uncertainty involved in the earthquake ground motion.

Sign in / Sign up

Export Citation Format

Share Document