Observation of 1- to 5-second microtremors and their application to earthquake engineering. Part I: Comparison with long-period accelerations at the Tokachi-oki earthquake of 1968

1978 ◽  
Vol 68 (3) ◽  
pp. 767-779
Author(s):  
Yutaka Ohta ◽  
Hiroshi Kagami ◽  
Noritoshi Goto ◽  
Kazuyoshi Kudo
Keyword(s):  
Earthquake Engineering ◽  
Underground Structure ◽  
Strong Motion ◽  
Period Range ◽  
Predominant Period ◽  
High Rise ◽  
Long Period ◽  
Short Period ◽  
Source And Path Effects ◽  
Observation Line

abstract A study on elucidation of possible amplification characteristic of strong motions due to deep situated deposit was made by means of 1 to 5 sec microtremors observation. At the Tokachi-oki earthquake of 1968 (M=7.9) several accelerograms were obtained, among which some are dominant but others are not significant in longer periods than 1 sec. To understand whether these differences are from source and path effects or site conditions is important for estimating seismic input motions to high-rise buildings. A long-period microtremors observation was introduced to pursue this problem. Observations were carried out in three cities where the typical acceleration records had been obtained, employing a specially designed instrument good for the microtremors with periods ranging from 0.5 to 6 sec. Each observation line was chosen so as to traverse the accelerograph site along which a remarkable geological change of the underground structure is expected, for example, from the outcrop of bedrock to the alluvial deposit. Through comparison of the obtained spectra and their peaks with those derived from the strong-motion records, it was derived that their predominancy and predominant period in the long-period range are clearly responsible to the presence of deep situated deposit. A formulation of observation and analysing procedures of the long-period microtremors was also proposed, paying attention to overcome the defects in the well-known technique for the short-period microtremors.

Approximate method to estimate the short-period strong motion spectra on bedrock

1981 ◽  
Vol 71 (2) ◽  
pp. 491-505
Author(s):  
Katsuhiko Ishida
Keyword(s):  
Earthquake Swarm ◽  
Strong Motion ◽  
Fourier Amplitude ◽  
Period Range ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Short Period ◽  
Amplitude Spectra ◽  
Low Pass ◽  
Parkfield Earthquake

abstract The methodology to estimate the strong motion Fourier amplitude spectra in a short-period range (T ≦ 1 to 2 sec) on a bedrock level is discussed in this paper. The basic idea is that the synthetic strong motion Fourier spectrum F˜A(ω) calculated from smoothed rupture velocity model (Savage, 1972) is approximately similar to that of low-pass-filtered strong earthquake ground motion at a site in a period range T ≧ 1 to 2 sec: F˜A(ω)=B˜(ω)·A(ω). B˜(ω) is an observed Fourier spectrum on a bedrock level and A(ω) is a low-pass filter. As a low-pass filter, the following relation, A ( T ) = · a · T n a T n + 1 , ( T = 2 π / ω ) , is assumed. In order to estimate the characteristic coefficients {n} and {a}, the Tokachi-Oki earthquake (1968), the Parkfield earthquake (1966), and the Matsushiro earthquake swarm (1966) were analyzed. The results obtained indicate that: (1) the coefficient {n} is nearly two for three earthquakes, and {a} is nearly one for the Tokachi-Oki earthquake, eight for the Parkfield earthquake, and four for the Matsushiro earthquake swarm, respectively; (2) the coefficient {a} is related with stress drop Δσ as (a = 0.07.Δσ). Using this relationship between {a} and Δσ, the coefficients {a} of past large earthquakes were estimated. The Fourier amplitude spectra on a bedrock level are also estimated using an inverse filtering method of A ( T ) = a T 2 a T 2 + 1 .

Continuous measurements of microtremors on sediments and basement in Los Angeles, California

1993 ◽  
Vol 83 (5) ◽  
pp. 1595-1609 ◽  
Author(s):  
Hiroaki Yamanaka ◽  
Marijan Dravinski ◽  
Hiroshi Kagami
Keyword(s):  
Los Angeles ◽  
Continuous Measurement ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Earthquake Ground Motion ◽  
Spectral Amplitude ◽  
Spectral Ratios ◽  
Long Period ◽  
Short Period ◽  
Deep Sediments

Abstract Continuous measurement of microtremors at two sites on basement rock and sediments was carried out in Los Angeles, California, in order to understand the fundamental characteristics of microtremors. A predominant peak with a period of about 6.5 sec was found in the microtremor spectra in both media. The spectral amplitude of the peaks varied gradually with time in a similar manner at the two sites. Their time-variant characteristics are in agreement with change in oceanic swell height observed at an oceanic buoy in the southwest of Los Angeles. This suggests that they originate from an oceanic disturbance. On the other hand, a clear daily variation of spectral amplitudes at a period of 0.3 sec indicates that short-period microtremors are caused by cultural noises. It was found that the spectral ratio of long-period microtremors between the basement and the sediments was repeatable, although the spectral amplitudes at the two sites were time-variant. The spectral ratio of the long-period microtremors was similar to that derived from strong motion records. This suggests the applicability of spectral ratios of microtremors to assess the effects of deep sediments on long-period earthquake ground motion.

Strong motion accelerograph records from the 1993 Napierville earthquake

1995 ◽  
Vol 22 (1) ◽  
pp. 190-196
Author(s):  
René Tinawi ◽  
André Filiatrault ◽  
Pierre Léger
Keyword(s):  
Ground Motion ◽  
Energy Content ◽  
Strong Motion ◽  
Response Spectra ◽  
High Energy ◽  
Period Range ◽  
Attenuation Relationships ◽  
Acceleration Time Histories ◽  
Short Period ◽  
Time Histories

An earthquake of magnitude ML = 4.3 occurred near Napierville, Quebec, on November 16, 1993. An accelerograph at the liquefaction, storage, and regasification plant of Gaz Metropolitain in Montreal, about 55 km from the epicentre, recorded the ground motion. Although the maximum accelerations and velocities from this event are small, the acceleration time histories do confirm the high energy content in the very short period range. The recorded ground motion and corresponding absolute acceleration response spectra are presented and various attenuation relationships, proposed for eastern North America, are utilized to compare the measured and predicted ground motion parameters. Key words: Napierville earthquake, attenuation relationships, acceleration spectra, strong motion records.

scholarly journals The February 9, 1971 San Fernando earthquake: A study of source finiteness in teleseismic body waves

1978 ◽  
Vol 68 (1) ◽  
pp. 1-29 ◽  
Author(s):  
Charles A. Langston
Keyword(s):  
Near Field ◽  
Dislocation Line ◽  
Strong Motion ◽  
Body Waves ◽  
P Waves ◽  
Long Period ◽  
Short Period ◽  
Wave Forms ◽  
San Fernando ◽  
The Time Domain

abstract Teleseismic P, SV, and SH waves recorded by the WWSS and Canadian networks from the 1971 San Fernando, California earthquake (ML = 6.6) are modeled in the time domain to determine detailed features of the source as a prelude to studying the near and local field strong-motion observations. Synthetic seismograms are computed from the model of a propagating finite dislocation line source embedded in layered elastic media. The effects of source geometry and directivity are shown to be important features of the long-period observations. The most dramatic feature of the model is the requirement that the fault, which initially ruptured at a depth of 13 km as determined from pP-P times, continuously propagated toward the free surface, first on a plane dipping 53°NE, then broke over to a 29°NE dipping fault segment. This effect is clearly shown in the azimuthal variation of both long period P- and SH-wave forms. Although attenuation and interference with radiation from the remainder of the fault are possible complications, comparison of long- and short-period P and short-period pP and P waves suggest that rupture was initially bilateral, or, possibly, strongly unilateral downward, propagating to about 15 km depth. The average rupture velocity of 1.8 km/sec is well constrained from the shape of the long-period wave forms. Total seismic moment is 0.86 × 1026 dyne-cm. Implications for near-field modeling are drawn from these results.

Significance of Ground Motion Scaling Parameters on Amplitude of Scale Factors and Seismic Response of Short- and Long-Period Structures

2019 ◽  
Vol 35 (4) ◽  
pp. 1663-1688 ◽  
Author(s):  
Esengul Cavdar ◽  
Gokhan Ozdemir ◽  
Beyhan Bayhan
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Ground Motions ◽  
Response Spectra ◽  
Scaling Method ◽  
Period Range ◽  
Long Period ◽  
Scale Factors ◽  
Short Period ◽  
Response History Analysis

In this study, an ensemble of ground motions is selected and scaled in order to perform code-compliant bidirectional Nonlinear Response History Analysis for the design purpose of both short- and long-period structures. The followed scaling method provides both the requirements of the Turkish Earthquake Code regarding the scaling of ground motions and compatibility of response spectra of selected ground motion pairs with the target spectrum. The effects of four parameters, involved in the followed scaling method, on both the amplitude of scale factors and seismic response of structures are investigated. These parameters are the number of ground motion records, period range, number of periods used in the related period range, and distribution of weight factors at the selected periods. In the analyses, ground motion excitations were applied to both fixed-base and seismically isolated structure models representative of short- and long-period structures, respectively. Results revealed that both the amplitudes of scale factors and seismic response of short-period structures are more prone to variation of investigated parameters compared to those of long-period structures.

Evaluation of the relation between near-surface geological units and ground response in the vicinity of Long Beach, California

1979 ◽  
Vol 69 (5) ◽  
pp. 1603-1622
Author(s):  
A. M. Rogers ◽  
J. C. Tinsley ◽  
W. W. Hays ◽  
K. W. King
Keyword(s):  
Strong Motion ◽  
Test Site ◽  
Peak Ground Velocity ◽  
Long Beach ◽  
Spectral Ratios ◽  
Low Velocity ◽  
Ground Response ◽  
Near Surface ◽  
Long Period ◽  
Short Period

abstract Simulataneous recordings of Nevada Test Site nuclear events were made at sites underlain by alluvium in the Long Beach, California, area and at sites underlain by rock in the Palos Verdes and Pasadena areas. These data show peak-ground-velocity alluvium-to-rock ratios as large as 7 and spectral ratios as high as 11 in the period band from 0.2 to 6 sec. Comparison of the low-strain nuclear-explosion data and the San Fernando earthquake strong-motion data at three sites indicates that the alluvium-to-rock spectral ratios derived from the nuclear explosions are similar to those derived from the earthquake. Significant trends exist in the short-period data, indicating higher ground response at sites underlain at the near-surface by materials that have high void ratios and lower ground response with increasing thickness of Quaternary deposits. These results suggest that the short-period response is primarily controlled both by near-surface low-velocity layers and by attenuation in the Quaternary sediments. Comparison of the data of this study with data collected in other areas indicates that the long-period response increase with either increasing depth to basement or with alluvium thickness, when this thickness is greater than 400 m. From previous theoretical studies and these results, ground response in the long-period band is related to those underlying geological structures and major velocity contrasts that control the development of surface waves.

Displacement Spectra for Long Periods

2004 ◽  
Vol 20 (2) ◽  
pp. 347-376 ◽  
Author(s):  
Ezio Faccioli ◽  
Roberto Paolucci ◽  
Julien Rey
Keyword(s):  
Strong Motion ◽  
Seismic Source ◽  
Response Spectra ◽  
Analytical Models ◽  
Elastic Displacement ◽  
Period Range ◽  
Motion Data ◽  
Displacement Spectra ◽  
Long Period ◽  
Displacement Response Spectra

Using selected sets of high-quality digital strong motion data from different regions (Taiwan, Japan, Italy, and Greece), the salient features of displacement response spectra in the long-period range are illustrated (up to 10 s period) as a function of magnitude, source distance, and site conditions. By means of simple analytical models of displacement waveforms, we have derived analytical expressions for the displacement spectra that provide satisfactory fits to the observations. These expressions also demonstrate that the moment magnitude and distance control the shape of the spectra consistent with the commonly accepted models of the seismic source. Furthermore, we derived from simple physical considerations an analytical expression of the variation of peak ground displacement with magnitude and distance that reasonably fits the observations. The findings of this study are believed to be particularly useful in the formulation of design elastic displacement spectra for seismic codes, and in zoning studies of seismic hazard for long-period structures.

scholarly journals Parkfield earthquake of June 28, 1966: Magnitude and source mechanism

1968 ◽  
Vol 58 (2) ◽  
pp. 689-709
Author(s):  
Francis T. Wu
Keyword(s):  
Love Wave ◽  
Main Shock ◽  
Near Field ◽  
Strong Motion ◽  
Wave Radiation ◽  
Motion Data ◽  
Long Period ◽  
Short Period ◽  
Double Couple ◽  
Parkfield Earthquake

Abstract The Parkfield earthquake of June 28, 1966 (04:26:12.4 GMT) is studied using short-period and long-period teleseismic records. It is found that (1) Mb = 5.8 and Ms = 6.4 as compared to Mb = 5.4 and Ms = 5.4 for the foreshock (04:08:54), (2) both the Rayleigh and Love wave radiation patterns conform to those of a double couple at a depth of about 8.6 km, (3) the main shock can be represented by a series of shocks separated in space and time. The near-field strong-motion data support the last conclusion. Based on strong-motion seismograms, and the surficial evidences of the dimensions of the fault, the energy is found to be 1021 ergs.

scholarly journals Strong ground motion of the San Fernando, California, earthquake: Ground displacements

1975 ◽  
Vol 65 (1) ◽  
pp. 193-225
Author(s):  
Thomas C. Hanks
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Strong Motion ◽  
Geological Structure ◽  
Period Range ◽  
Long Period ◽  
Wave Forms ◽  
San Fernando ◽  
Displacement Wave ◽  
Strong Ground

abstract Two hundred and thirty-four components of ground displacement are the basis of an investigation of long-period strong ground motion in southern California arising from the San Fernando, California, earthquake. The displacement data are obtained from the double integration of strong-motion accelerograms via the base-line adjustment and filtering operations routinely performed in the series “Strong Motion Earthquake Accelerograms”. These procedures can recover long-period data from strong-motion accelerograms with considerable accuracy. Many-station comparisons of displacement data for which the station spacing is small compared to the wavelengths of interest reveal that uncertainties in displacement are less than 1 cm in the period range 5 to 8 sec, 1 to 2 cm at periods near 10 sec, and 2 to 4 cm in the period range 10 to 15 sec, for a data sensitivity of approximately 7.6 cm/g. For limited variations in epicentral distance (R) and source-station azimuth (ϕ), ground displacements show a strong coherence; for wider variations in R and ϕ, many of the observed variations in the displacement wave forms are easily attributable to well-understood seismological phenomena. Seismic moment, source dimension, radiation pattern, rupture propagation, the development of surface waves and their subsequent dispersion, and azimuthal variations in the gross geological structure all appear to have first-order significance in fashioning the gross amplitude and frequency content of the displacement wave forms and in explaining observed variations with R and ϕ. The essential simplicity of these displacement wave forms offers considerable optimism that long-period strong ground motion can be realistically synthesized with advance knowledge of the earthquake source parameters and gross geological structure.

Observation of 1- to 5-second microtremors and their application to earthquake engineering. Part II. Evaluation of site effect upon seismic wave amplification due to extremely deep soil deposits

1982 ◽  
Vol 72 (3) ◽  
pp. 987-998
Author(s):  
Hiroshi Kagami ◽  
C. Martin Duke ◽  
George C. Liang ◽  
Yutaka Ohta
Keyword(s):  
Los Angeles ◽  
Earthquake Engineering ◽  
Large Scale ◽  
Strong Motion ◽  
Basement Rock ◽  
Deep Soil ◽  
Large Scale Structures ◽  
Seismic Input ◽  
Long Period ◽  
Scale Structures

abstract The usefulness of long-period microtremor observation for earthquake engineering problems at extremely deep soil deposit site was examined in this study. Microtremor observations were made in the Niigata Plain, Japan, and in Los Angeles, California, where depths to the basement rock are several kilometers. These two locations were selected because strong-motion records obtained during the Niigata earthquake of 1964 and the San Fernando earthquake of 1971 contain large long-period amplitudes. Understanding why these predominate long-period motions were recorded is important for the evaluation of seismic input motions for large-scale structures. Long-period microtremor observations were carried out in both areas in order to evaluate the characteristics of deep soil. Observations were performed simultaneously at a number of stations to distinguish the nature of deep soil deposit. The result of Fourier analysis showed that amplitude of microtremors in long-period range increases systematically from the point of basement rock outcrop to deep deposit site, with the increase corresponding to the depth-to-basement rock. This relationship coincides with that observed in the strong-motion earthquake records. These analyses indicated that simultaneous observation of long-period microtremors at a number of stations can provide insight to the characteristic of deep soil amplification and, therefore, permit estimation of seismic input motions for large-scale structures.

Sign in / Sign up

Export Citation Format

Share Document