scholarly journals Teleseismic and strong-motion source spectra from two earthquakes in eastern Taiwan

1989 ◽  
Vol 79 (4) ◽  
pp. 935-944
Author(s):  
Lorraine J. Hwang ◽  
Hiroo Kanamori
Keyword(s):  
Hard Rock ◽  
Strong Motion ◽  
Reference Spectrum ◽  
Spectral Signatures ◽  
Motion Data ◽  
First Motion ◽  
Main Portion ◽  
Source Spectra ◽  
Rock Site ◽  
The Relationship

Abstract The 20 May and 14 November 1986 Hualien earthquakes occurred in a seismically active region of Taiwan. Locally determined focal mechanisms and aftershock patterns from the Taiwan Telemetered Seismographic Network indicate that both earthquakes occurred on steeply dipping reverse faults that trend NNE. This agrees with teleseismic first-motion data for the May event but not for the November event. This discrepancy is due to a moderate foreshock before the November event. Surface-wave analysis gives a solution for the November event of: dip 57°, rake 100°, and strike 43°, which is similar to the locally reported focal mechanism. The seismic moment of the November event is M0 = 1.7 × 1027 dynecm and the magnitudes determined from WWSSN data are m^b = 6.4, Ms = 7.3. Teleseismic source spectra show that the two events also have similar spectral signatures above 0.15 Hz. Reference acceleration spectra are computed from the average teleseismic source spectra and compared to the averaged acceleration spectra computed from strong-motion stations for both events. Correlations between the spectral amplitudes of the strong-motion spectra obtained from the main portion of the SMART 1 array and the teleseismically estimated reference spectra are poor above 0.2 Hz. Data from the hard-rock site situated outside of the basin indicates that amplification of the ground motion between 0.17-1.7 Hz is due to the alluvial valley where the SMART 1 array is located. The amplitude of the observed spectrum is five times the reference spectrum at the hard-rock site. This is consistent with similar observations from the 1985 Michoacan and 1983 Akita-Oki earthquakes. The analysis of these and more teleseismic and strong-motion records will lead to a better understanding of the relationship between their spectra.

scholarly journals Comparison of strong-motion spectra with teleseismic spectra for three magnitude 8 subduction-zone earthquakes

1990 ◽  
Vol 80 (4) ◽  
pp. 913-934
Author(s):  
Heidi Houston ◽  
Hiroo Kanamori
Keyword(s):  
Half Space ◽  
Site Response ◽  
Strong Motion ◽  
Body Waves ◽  
Reference Spectrum ◽  
Empirical Relations ◽  
Finite Fault ◽  
Simple Physical Model ◽  
Source Spectra ◽  
The Difference

Abstract We studied strong-motion spectra observed for three Mw 7.8 to 8.0 earthquakes (the 1985 Michoacán, Mexico; 1985 Valparaíso, Chile; and 1983 Akita-Oki, Japan earthquakes). We determined the decay of spectral amplitude with distance from the station, considering different measures of distance from a finite fault. We compared strong-motion spectra (Fourier acceleration spectra) observed for these three earthquakes with those estimated from the source spectrum determined from teleseismic P waves. We scaled the teleseismic source spectra to produce reference strong-motion spectra at periods from 1 to 10 sec using a simple physical model of far-field S body waves from a point source recorded at the surface of a homogeneous half-space. For all three earthquakes the reference spectral amplitudes at periods of 1 to 5 sec are about half the observed ones at distances of about 50 km. The difference increases as the distance increases. At distances of 200 to 300 km, the reference spectrum is about 1/10 of the observed one. The difference between the reference and the observed spectrum is attributed to the contribution of phases other than direct S waves and to site response. We applied corrections for the finiteness (spatial extent) of the source using a simple model of rupture propagation on a dipping two-dimensional fault. Including the source finiteness did not improve the estimate substantially at periods from 1 to 20 sec, but it modeled significant changes in the signal duration as a function of azimuth for the 1985 Michoacán earthquake. Our results can be used to establish empirical relations between the observed spectra and the half-space responses, depending on the distance and the site condition. If such empirical relations can be established, source spectra determined from teleseismic records may be used to estimate strong motions.

Processed strong-motion data for the El Salvador earthquake of June 19, 1982

1988 ◽  
Author(s):  
Kenneth W. Campbell ◽  
Sylvester Theodore Algermissen
Keyword(s):  
El Salvador ◽  
Strong Motion ◽  
Strong Motion Data ◽  
Motion Data

Duration prediction of Chilean strong motion data using machine learning

2021 ◽  
Vol 109 ◽  
pp. 103253
Author(s):  
Sarit Chanda ◽  
M.C. Raghucharan ◽  
K.S.K. Karthik Reddy ◽  
Vasudeo Chaudhari ◽  
Surendra Nadh Somala
Keyword(s):  
Machine Learning ◽  
Strong Motion ◽  
Strong Motion Data ◽  
Motion Data ◽  
Duration Prediction

Re-digitization of Strong Motion Data Recorded by SMAC-M Accelerographs

2021 ◽  
Vol 21 (1) ◽  
pp. 1_25-1_45
Author(s):  
Toshihide KASHIMA ◽  
Shin KOYAMA ◽  
Hiroto NAKAGAWA
Keyword(s):  
Strong Motion ◽  
Strong Motion Data ◽  
Motion Data

A comparison of two methods for earthquake source inversion using strong motion seismograms

1994 ◽  
Vol 37 (6) ◽  
Author(s):  
B. P. Cohee ◽  
G. C. Beroza
Keyword(s):  
Rise Time ◽  
Seismic Moment ◽  
Strong Motion ◽  
Rupture Time ◽  
Rupture Propagation ◽  
Rupture Velocity ◽  
Strong Motion Data ◽  
Motion Data ◽  
Inversion Methods ◽  
Window Method

In this paper we compare two time-domain inversion methods that have been widely applied to the problem of modeling earthquake rupture using strong-motion seismograms. In the multi-window method, each point on the fault is allowed to rupture multiple times. This allows flexibility in the rupture time and hence the rupture velocity. Variations in the slip-velocity function are accommodated by variations in the slip amplitude in each time-window. The single-window method assumes that each point on the fault ruptures only once, when the rupture front passes. Variations in slip amplitude are allowed and variations in rupture velocity are accommodated by allowing the rupture time to vary. Because the multi-window method allows greater flexibility, it has the potential to describe a wider range of faulting behavior; however, with this increased flexibility comes an increase in the degrees of freedom and the solutions are comparatively less stable. We demonstrate this effect using synthetic data for a test model of the Mw 7.3 1992 Landers, California earthquake, and then apply both inversion methods to the actual recordings. The two approaches yield similar fits to the strong-motion data with different seismic moments indicating that the moment is not well constrained by strong-motion data alone. The slip amplitude distribution is similar using either approach, but important differences exist in the rupture propagation models. The single-window method does a better job of recovering the true seismic moment and the average rupture velocity. The multi-window method is preferable when rise time is strongly variable, but tends to overestimate the seismic moment. Both methods work well when the rise time is constant or short compared to the periods modeled. Neither approach can recover the temporal details of rupture propagation unless the distribution of slip amplitude is constrained by independent data.

Frequency-dependent attenuation of shear waves in the crust of the southern Kanto area, Japan

1994 ◽  
Vol 84 (5) ◽  
pp. 1387-1396
Author(s):  
Shigeo Kinoshita
Keyword(s):  
Shear Waves ◽  
Strong Motion ◽  
Body Waves ◽  
Philippine Sea Plate ◽  
Eurasian Plate ◽  
Philippine Sea ◽  
Motion Data ◽  
Basement Rocks ◽  
Acceleration Data ◽  
Attenuation Characteristics

Abstract The attenuation characteristics of shear waves in the crust of the southern Kanto area, central Japan, were estimated using strong-motion data, including acceleration data recorded in the pre-Tertiary basement rocks by means of downhole observation. The quality factor Qs(f) was determined for a range of discrete frequencies from 0.5 to 16 Hz from the analysis of data from 13 local earthquakes with focal depths of less than about 50 km that occurred in the Philippine Sea plate and in the boundary zone between the lower part of the Eurasian plate and the upper part of the Philippine Sea plate. The estimated 1/Qs(f) shows a peaked structure in this frequency range on the assumption that the geometrical spreading exponent is -1 (body waves). The estimated peak 1/Qs(f) is of the order of 10-2 at 0.8 Hz.

Peak horizontal acceleration and velocity from strong-motion records including records from the 1979 imperial valley, California, earthquake

1981 ◽  
Vol 71 (6) ◽  
pp. 2011-2038 ◽  
Author(s):  
William B. Joyner ◽  
David M. Boore
Keyword(s):  
Strong Motion ◽  
Fault Rupture ◽  
Imperial Valley ◽  
Attenuation Relations ◽  
Motion Data ◽  
Horizontal Acceleration ◽  
Anelastic Attenuation ◽  
Distance Dependence ◽  
Peak Horizontal Acceleration

Abstract We have taken advantage of the recent increase in strong-motion data at close distances to derive new attenuation relations for peak horizontal acceleration and velocity. This new analysis uses a magnitude-independent shape, based on geometrical spreading and anelastic attenuation, for the attenuation curve. An innovation in technique is introduced that decouples the determination of the distance dependence of the data from the magnitude dependence. The resulting equations are log A = − 1.02 + 0.249 M − log r − 0.00255 r + 0.26 P r = ( d 2 + 7.3 2 ) 1 / 2 5.0 ≦ M ≦ 7.7 log V = − 0.67 + 0.489 M − log r − 0.00256 r + 0.17 S + 0.22 P r = ( d 2 + 4.0 2 ) 1 / 2 5.3 ≦ M ≦ 7.4 where A is peak horizontal acceleration in g, V is peak horizontal velocity in cm/ sec, M is moment magnitude, d is the closest distance to the surface projection of the fault rupture in km, S takes on the value of zero at rock sites and one at soil sites, and P is zero for 50 percentile values and one for 84 percentile values. We considered a magnitude-dependent shape, but we find no basis for it in the data; we have adopted the magnitude-independent shape because it requires fewer parameters.

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