scholarly journals SCALING LAW OF SHORT-PERIOD SOURCE SPECTRA FOR CRUSTAL EARTHQUAKES IN JAPAN CONSIDERING STYLE OF FAULTING OF DIP-SLIP AND STRIKE-SLIP

2010 ◽  
Vol 75 (651) ◽  
pp. 923-932 ◽  
Author(s):  
Toshimi SATOH
Keyword(s):  
Scaling Law ◽  
Strike Slip ◽  
Crustal Earthquakes ◽  
Short Period ◽  
Source Spectra

Horizontal particle velocity and its relation to magnitude in the Western United States

1979 ◽  
Vol 69 (6) ◽  
pp. 2037-2061
Author(s):  
A. F. Espinosa
Keyword(s):  
United States ◽  
Data Base ◽  
San Francisco ◽  
Seismic Waves ◽  
Scaling Law ◽  
Direct Determination ◽  
Strong Motion ◽  
Western United States ◽  
Short Period ◽  
Horizontal Particle

abstract A magnitude (ML) scaling law has been derived from the strong-motion data base of the San Fernando earthquake of February 9, 1971, and the results have been compared with other strong-motion recordings obtained from 62 earthquakes in the Western United States. The relationship derived is ML = 3.21 + 1.35 log10Δ + log10v. An excellent agreement was obtained between the determined ML values in this study and those evaluated by Kanamori and Jennings (1978). This scaling law is applicable to the collected data from 63 earthquakes whose local magnitudes range from about 4.0 to 7.2, recorded at epicentral distances between about 5 to 300 km, and with short-period seismic waves in the range of 0.2 to 3.0 sec. The Long Beach earthquake of 1933, with an ML = 6.3 (PAS) and an ML = 6.43 ± 0.36 as determined by Kanamori and Jennings is in agreement with an ML = 6.49 ± 0.32 obtained in this study. The Imperial Valley earthquake of 1940, with an ML = 6.5 (PAS), compares well with an ML = 6.5 as determined in this study. The Kern County earthquake of 1952, with an ML = 7.2 (BRK), is in fairly good agreement with the ML = 7.0 ± 0.2 obtained in this investigation. This value is significantly lower than the commonly quoted 7.7 value for this event. The San Francisco earthquake of 1957, with an ML = 5.3 (BRK), agrees very well with an ML = 5.3 ± 0.1 as determined in this study. The Parkfield earthquake of 1966 has an ML = 5.8 ± 0.3, which is consistent with the 5.6 (PAS). The procedure developed here is applied to the data base obtained from the Western United States strong-motion recordings. The procedure allows the evaluation of ML for moderate and larger earthquakes from the first integration of the strong-motion accelerograms and allows the direct determination of ML from the scaled amplitudes in a rapid, economical, and accurate manner. It also has allowed for the extension of the trend of the attenuation curve for horizontal particle velocities at distances less than 5 km for different size events.

Aftershocks and surface faulting associated with the intraplate Guinea, West Africa, earthquake of 22 December 1983

1987 ◽  
Vol 77 (5) ◽  
pp. 1579-1601
Author(s):  
C. J. Langer ◽  
M. G. Bonilla ◽  
G. A. Bollinger
Keyword(s):  
West Africa ◽  
Focal Mechanism ◽  
Main Shock ◽  
Strike Slip ◽  
Fault System ◽  
Epicentral Area ◽  
Lateral Strike Slip ◽  
Focal Mechanism Solutions ◽  
Short Period ◽  
East West

Abstract This study reports on the results of geological and seismological field studies conducted following the rare occurrence of a moderate-sized West African earthquake (mb = 6.4) with associated ground breakage. The epicentral area of the northwestern Guinea earthquake of 22 December 1983 is a coastal margin, intraplate locale with a very low level of historical seismicity. The principal results include the observation that seismic faulting occurred on a preexisting fault system and that there is good agreement among the surface faulting, the spatial distribution of the aftershock hypocenters, and the composite focal mechanism solutions. We are not able, however, to shed any light on the reason(s) for the unexpected occurrence of this intraplate earthquake. Thus, the significance of this study is its contribution to the observational datum for such earthquakes and for the seismicity of West Africa. The main shock was associated with at least 9 km of surface fault-rupture. Trending east-southeast to east-west, measured fault displacements up to ∼13 cm were predominantly right-lateral strike slip and were accompanied by an additional component (5 to 7 cm) of vertical movement, southwest side down. The surface faulting occurred on a preexisting fault whose field characteristics suggest a low slip rate with very infrequent earthquakes. There were extensive rockfalls and minor liquefaction effects at distances less than 10 km from the surface faulting and main shock epicenter. Main shock focal mechanism solutions derived from teleseismic data by other workers show a strong component of normal faulting motion that was not observed in the ground ruptures. A 15-day period of aftershock monitoring, commencing 22 days after the main shock, was conducted. Eleven portable, analog short-period vertical seismographs were deployed in a network with an aperture of 25 km and an average station spacing of 7 km. Ninety-five aftershocks were located from the more than 200 recorded events with duration magnitudes of about 1.5 or greater. Analysis of a selected subset (91) of those events define a tabular aftershock volume (26 km long by 14 km wide by 4 km thick) trending east-southeast and dipping steeply (∼60°) to the south-southwest. Composite focal mechanisms for groups of events, distributed throughout the aftershock volume, exhibit right-lateral, strike-slip motion on subvertical planes that strike almost due east. Although the general agreement between the field geologic and seismologic results is good, our preferred interpretation is for three en-echelon faults striking almost due east-west.

An NGA Empirical Model for Estimating the Horizontal Spectral Values Generated by Shallow Crustal Earthquakes

2008 ◽  
Vol 24 (1) ◽  
pp. 217-242 ◽  
Author(s):  
I. M. Idriss
Keyword(s):  
Empirical Model ◽  
Standard Error ◽  
Strike Slip ◽  
Model Parameters ◽  
Ground Acceleration ◽  
Site Specific ◽  
Crustal Earthquakes ◽  
Average Shear ◽  
Error Terms ◽  
New Generation

An empirical model for estimating the horizontal pseudo absolute spectral accelerations (PSA) generated by shallow crustal earthquakes is presented in this paper. The model was selected to be simple and the model parameters were estimated using the recordings gathered as part of the New Generation Attenuation (NGA) project. These parameters are presented for sites with an average shear wave velocity in the upper 30 m, VS30>900 m/s, and for sites with 450 m/s≤ VS30≤900 m/s. Site-specific dynamic response calculations are recommended for estimating spectral ordinates for sites with VS30≤180 m/s. Parameters for sites with 180 m/s< VS30<450 m/s are not included in this paper. The median values of peak horizontal ground acceleration (PGA) and PSA for short periods are on the order of 15% to 20% lower for strike slip events and 30% to 40% lower for reverse events than those calculated using pre-NGA relationships. The differences decrease significantly at longer periods. The minimum values of the standard error terms (for moment magnitude, M≥7.5) are about 15% to 30% larger and the maximum values of the standard error terms (for M≤5) are about 2% to 12% larger than the pre-NGA values.

Study of the tsunami source in the Palu Bay following the Mw7.5 2018 Sulawesi earthquake

2020 ◽  
Author(s):  
Fabrizio Romano ◽  
Haider Hasan ◽  
Stefano Lorito ◽  
Finn Løvholt ◽  
Beatriz Brizuela ◽  
...  
Keyword(s):  
Tide Gauge ◽  
Joint Inversion ◽  
Seismic Source ◽  
Strike Slip ◽  
Tsunami Source ◽  
Fault System ◽  
Tsunami Propagation ◽  
Slip Mechanism ◽  
Short Period ◽  
Nonlinear Joint

&lt;p&gt;On 28 September 2018 a Mw 7.5 strike-slip earthquake occurred on the Palu-Koro fault system in the Sulawesi Island. Immediately after the earthquake a powerful tsunami hit the Palu Bay causing large damages and numerous fatalities.&lt;/p&gt;&lt;p&gt;Several works, inverting seismic or geodetic data, clearly estimated the slip distribution of this event, but the causative source of the tsunami is still not completely understood; indeed, the strike-slip mechanism of the seismic source alone might not be sufficient to explain the large runups observed (&gt; 6 m) along the coast of the Palu Bay, and thus one or more additional non-seismic sources like a landslide could have contributed to generate the big tsunami. An insight of that can be found in an extraordinary collection of amateur videos, and on the only available tide gauge in the Bay, at Pantoloan, that showed evidence for a short period wave of at least 2-3 minutes, compatible with a landslide.&lt;/p&gt;&lt;p&gt;In this study, we attempt to discriminate the contribution in the tsunami generation of both the seismic source and &amp;#160;some supposed landslides distributed along the coast of the Bay.&lt;/p&gt;&lt;p&gt;In particular, we attempt to estimate the causative source of the tsunami by means of a nonlinear joint inversion of geodetic (InSAR) and runup data. We use a fault geometry consistent with the Sentinel-2 optical analysis results and analytically compute the geodetic Green&amp;#8217;s functions. The same fault model is used to compute the initial condition for the seismic tsunami Green&amp;#8217;s functions, including the contribution of the horizontal deformation due to the gradient of the bathymetry (10 m spatial resolution); the landslide tsunami Green&amp;#8217;s functions are computed the software BingClaw by placing several hypothetical sources in the Bay. In both the cases the tsunami propagation is modelled by numerically solving the nonlinear shallow water equations.&lt;/p&gt;&lt;p&gt;In this work we also attempt to address the validity of Green&amp;#8217;s functions approach (linearity) for earthquake and landslide sources as well as the wave amplitude offshore as predictor of nearby runup.&lt;/p&gt;

Comparisons of the NGA Ground-Motion Relations

2008 ◽  
Vol 24 (1) ◽  
pp. 45-66 ◽  
Author(s):  
Norman Abrahamson ◽  
Gail Atkinson ◽  
David Boore ◽  
Yousef Bozorgnia ◽  
Kenneth Campbell ◽  
...  
Keyword(s):  
Site Response ◽  
Strike Slip ◽  
Data Sets ◽  
Sediment Depth ◽  
Long Period ◽  
Crustal Earthquakes ◽  
Nonlinear Site Response ◽  
Soil Sediment ◽  
Active Tectonic ◽  
Standard Deviations

The data sets, model parameterizations, and results from the five NGA models for shallow crustal earthquakes in active tectonic regions are compared. A key difference in the data sets is the inclusion or exclusion of aftershocks. A comparison of the median spectral values for strike-slip earthquakes shows that they are within a factor of 1.5 for magnitudes between 6.0 and 7.0 for distances less than 100 km. The differences increase to a factor of 2 for M5 and M8 earthquakes, for buried ruptures, and for distances greater than 100 km. For soil sites, the differences in the modeling of soil/sediment depth effects increase the range in the median long-period spectral values for M7 strike-slip earthquakes to a factor of 3. The five models have similar standard deviations for M6.5-M7.5 earthquakes for rock sites and for soil sites at distances greater than 50 km. Differences in the standard deviations of up to 0.2 natural log units for moderate magnitudes at all distances and for large magnitudes at short distances result from the treatment of the magnitude dependence and the effects of nonlinear site response on the standard deviation.

scholarly journals Empirical Correlations between Peak Ground Velocity and Spectrum-Based Intensity Measures

2012 ◽  
Vol 28 (1) ◽  
pp. 17-35 ◽  
Author(s):  
Brendon A. Bradley
Keyword(s):  
Ground Motion ◽  
Peak Ground Velocity ◽  
Strongly Correlated ◽  
Correlation Equations ◽  
Ground Acceleration ◽  
Intensity Measures ◽  
Ground Motion Selection ◽  
Crustal Earthquakes ◽  
Short Period ◽  
Spectrum Intensity

Empirical correlation equations between peak ground velocity ( PGV) and several spectrum-based ground motion intensity measures are developed. The intensity measures examined in particular were: peak ground acceleration ( PGA), 5% damped pseudo-spectral acceleration ( SA), acceleration spectrum intensity ( ASI), and spectrum intensity ( SI). The computed correlations were obtained using ground motions from active shallow crustal earthquakes and four ground motion prediction equations. Results indicate that PGV is strongly correlated (i.e., a correlation coefficient of [Formula: see text]) with SI, moderately correlated with medium to long-period SA (i.e., [Formula: see text] for vibration periods 0.5-3.0 seconds), and also moderately correlated with short period SA, PGA and ASI ([Formula: see text]). A simple example is used to illustrate one possible application of the developed correlation equations for ground motion selection.

Summary of the Abrahamson & Silva NGA Ground-Motion Relations

2008 ◽  
Vol 24 (1) ◽  
pp. 67-97 ◽  
Author(s):  
Norman Abrahamson ◽  
Walter Silva
Keyword(s):  
Standard Deviation ◽  
Ground Motion ◽  
Site Response ◽  
Hanging Wall ◽  
Site Location ◽  
Crustal Earthquakes ◽  
Nonlinear Site Response ◽  
Short Period ◽  
Standard Deviations ◽  
Improved Model

Empirical ground-motion models for the rotation-independent average horizontal component from shallow crustal earthquakes are derived using the PEER NGA database. The model is applicable to magnitudes 5–8.5, distances 0–200 km, and spectral periods of 0–10 sec. In place of generic site categories (soil and rock), the site is parameterized by average shear-wave velocity in the top 30 m ( VS30) and the depth to engineering rock (depth to VS=1000 m/s). In addition to magnitude and style-of-faulting, the source term is also dependent on the depth to top-of-rupture: for the same magnitude and rupture distance, buried ruptures lead to larger short-period ground motions than surface ruptures. The hanging-wall effect is included with an improved model that varies smoothly as a function of the source properties (M, dip, depth), and the site location. The standard deviation is magnitude dependent with smaller magnitudes leading to larger standard deviations. The short-period standard deviation model for soil sites is also distant-dependent due to nonlinear site response, with smaller standard deviations at short distances.

Source Parameters of Weak Crustal Earthquakes of the Vrancea Region from Short-period Waveform Inversion

2005 ◽  
Vol 162 (3) ◽  
pp. 495-513 ◽  
Author(s):  
Luminita Ardeleanu ◽  
Mircea Radulian ◽  
Jan Šílený ◽  
Giuliano Francesco Panza
Keyword(s):  
Source Parameters ◽  
Waveform Inversion ◽  
Crustal Earthquakes ◽  
Short Period ◽  
Vrancea Region

Inversion of regional surface-wave spectra for source parameters of aftershocks from the Loma Prieta earthquake

1991 ◽  
Vol 81 (5) ◽  
pp. 1726-1736
Author(s):  
Susan L. Beck ◽  
Howard J. Patton
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Focal Mechanism ◽  
Source Parameters ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
P Wave ◽  
Wave Spectra ◽  
Short Period ◽  
First Motion

Abstract Surface waves recorded at regional distances are used to study the source parameters for three of the larger aftershocks of the 18 October 1989, Loma Prieta, California, earthquake. The short-period P-wave first-motion focal mechanisms indicate a complex aftershock sequence with a wide variety of mechanisms. Many of these events are too small for teleseismic body-wave analysis; therefore, the regional surface-waves provide important long-period information on the source parameters. Intermediate-period Rayleigh- and Love-wave spectra are inverted for the seismic moment tensor elements at a fixed depth and repeated for different depths to find the source depth that gives the best fit to the observed spectra. For the aftershock on 19 October at 10:14:35 (md = 4.2), we find a strike-slip focal mechanism with right lateral motion on a NW-trending vertical fault consistent with the mapped trace of the local faults. For the aftershock on 18 October at 10:22:04 (md = 4.4), the surface waves indicate a pure reverse fault with the nodal planes striking WNW. For the aftershock on 19 October at 09:53:50 (md = 4.4), the surface waves indicate a strike-slip focal mechanism with a NW-trending vertical nodal plane consistent with the local strike of the San Andreas fault. Differences between the surface-wave focal mechanisms and the short-period P-wave first-motion mechanisms are observed for the aftershocks analyzed. This discrepancy may reflect the real variations due to differences in the band width of the two observations. However, the differences may also be due to (1) errors in the first-motion mechanism due to incorrect near-source velocity structure and (2) errors in the surface-wave mechanisms due to inadequate propagation path corrections.

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