Local magnitudes, seismic moments, and coda durations for earthquakes near Oroville, California

1977 ◽  
Vol 67 (3) ◽  
pp. 615-629 ◽  
Author(s):  
W. H. Bakun ◽  
A. G. Lindh
Keyword(s):  
Seismic Moment ◽  
Vertical Component ◽  
Local Magnitude ◽  
Short Period ◽  
Rms Error ◽  
Point Of Intersection ◽  
Epicentral Region

abstract Seismic moments Mo and local magnitudes ML for earthquakes near Oroville, California imply the linear log seismic moment-local magnitude relation log ⁡ 10 ( M o ) = ( 1.21 ± 0.03 ) M L + ( 17.02 ± 0.07 ) for 17 < log 10 M o < 25. Coda durations τ for short-period, vertical-component seismographs located in the epicentral region are related to local magnitude using two linear log τ-ML segments with point of intersection at ML ≂ 1.5. The rms error is 0.1 to 0.2 units of magnitude. A relation of the form log Mo = a1 + a3 (log τ)2 is sufficient (in the sense that rms error in log10Mo is 0.2 to 0.3 units) to relate τ and Mo for 18 ≦ log10Mo < 22. Coefficients for the above τ-ML and τ-Mo relationships are established for three seismographs of differing response

scholarly journals Local magnitude scale in Slovenia

2013 ◽  
Vol 34 ◽  
pp. 23-28 ◽  
Author(s):  
J. Bajc ◽  
Ž. Zaplotnik ◽  
M. Živčić ◽  
M. Čarman
Keyword(s):  
Vertical Component ◽  
Large Data ◽  
Least Square Method ◽  
Least Square ◽  
Magnitude Scale ◽  
Local Magnitude ◽  
Data Set ◽  
Seismic Stations ◽  
Short Period ◽  
Environment Agency

Abstract. In the paper a calibration study of the local magnitude scale in Slovenia is presented. The Seismology and Geology Office of the Slovenian Environment Agency routinely reports the magnitudes MLV of the earthquakes recorded by the Slovenian seismic stations. The magnitudes are computed from the maximum vertical component of the ground velocity with the magnitude equation that was derived some thirty years ago by regression analysis of the magnitudes recorded by a Wood-Anderson seismograph in Trieste and a short period seismograph in Ljubljana. In the study the present single magnitude MLV equation is replaced by a general form of the Richter local magnitude MWA equation. The attenuation function and station-component corrections that compensate the local effects near seismic stations are determined from the synthetic Wood-Anderson seismograms of a large data set by iterative least-square method. The data set used consists of approximately 18 000 earthquakes during a period of 14 yr, each digitally recorded on up to 29 stations. The derived magnitude equation is used to make the final comparison between the new MWA magnitudes and the routinely calculated MLV magnitudes. The results show good overall accordance between both magnitude equations. The main advantage of the introduction of station-component corrections is the reduced uncertainty of the local magnitude that is assigned to a certain earthquake.

Seismicity of the southeastern United States

1973 ◽  
Vol 63 (5) ◽  
pp. 1785-1808
Author(s):  
G. A. Bollinger
Keyword(s):  
United States ◽  
South Carolina ◽  
Southeastern United States ◽  
Vertical Component ◽  
Seismic Zone ◽  
Local Magnitude ◽  
Short Period ◽  
Central United States ◽  
Order Of Magnitude ◽  
Attenuation Characteristics

abstract Review and analysis of the existing data base for southeastern United States earthquakes indicate that the spatial pattern of energy release can be interpreted to occur in zones both parallel (southern Appalachian seismic zone) and transverse (central Virginia and South Carolina-Georgia seismic zones) to the regional Appalachian structural trend. The temporal pattern, for events V ≦ Io ≦ VIII, can be expressed by the recursion relationship, log N = 3.01 − 0.59 Io. Felt areas are, in general, one order of magnitude greater than for similar west coast events. Their configuration is elliptical and aligned with regional structure, except in central Virginia and Alabama and in coastal South Carolina. These latter areas have circular or lobate felt areas that may be caused by differences in focal depths and/or focal mechanisms. A tentative local magnitude formula is developed that employs the vertical component of the short-period Lg phase. It appears that the regional attenuation characteristics of this phase are similar to those found by Nuttli (1973a) in the central United States.

scholarly journals Dynamics of Comets

1992 ◽  
Vol 152 ◽  
pp. 255-268 ◽  
Author(s):  
A. Carusi ◽  
G.B. Valsecchi
Keyword(s):  
Molecular Clouds ◽  
Vertical Component ◽  
The Sun ◽  
Giant Molecular Clouds ◽  
Mean Motion Resonances ◽  
Galactic Field ◽  
Mean Motion ◽  
Short Period ◽  
Gravitational Processes

The gravitational processes affecting the dynamics of comets are reviewed. At great distances from the Sun the motion of comets is primarily affected by the vertical component of the galactic field, as well as by encounters with stars and giant molecular clouds. When comets move in the region of the planets, encounters with these can strongly affect their motion. A good fraction of all periodic comets spend some time in temporary libration about mean motion resonances with Jupiter; some comets can be captured by this planet as temporary satellites. Finally, there is a small number of objects with orbital characteristics quite different from those of all other short-period comets.

scholarly journals Local magnitude, duration magnitude and seismic moment of Dahshour 1992 earthquakes

2009 ◽  
Vol 43 (1) ◽  
Author(s):  
M. M. Dessokey ◽  
H. M. Hussein ◽  
E. M. Abdelrahman ◽  
M. F. Abdelwahed
Keyword(s):  
Seismic Moment ◽  
Local Magnitude ◽  
Duration Magnitude

scholarly journals Analysis of strong-motion data of the 1990 Eastern Sicily earthquake

1995 ◽  
Vol 38 (2) ◽  
Author(s):  
M. Di Bona ◽  
M. Cocco ◽  
A. Rovelli ◽  
R. Berardi ◽  
E. Boschi
Keyword(s):  
Frequency Band ◽  
Stress Drop ◽  
Seismic Moment ◽  
Ground Motions ◽  
Broad Band ◽  
Strong Motion ◽  
Moment Magnitude ◽  
Corner Frequency ◽  
Local Magnitude ◽  
The Moment

The strong motion accelerograms recorded during the 1990 Eastern Sicily earthquake have been analyzed to investigate source and attenuation parameters. Peak ground motions (peak acceleration, velocity and displacement) overestimate the values predicted by the empirical scaling law proposed for other Italian earthquakes, suggesting that local site response and propagation path effects play an important role in interpreting the observed time histories. The local magnitude, computed from the strong motion accelerograms by synthesizing the Wood-Anderson response, is ML = 5.9, that is sensibly larger than the local magnitude estimated at regional distances from broad-band seismograms (ML = 5.4). The standard omega-square source spectral model seems to be inadequate to describe the observed spectra over the entire frequency band from 0.2 to 20 Hz. The seismic moment estimated from the strong motion accelerogram recorded at the closest rock site (Sortino) is Mo = 0.8 x 1024 dyne.cm, that is roughly 4.5 times lower than the value estimated at regional distances (Mo = 3.7 x 1024 dyne.cm) from broad-band seismograms. The corner frequency estimated from the accelera- tion spectra i.5 J; = 1.3 Hz, that is close to the inverse of the dUl.ation of displacement pulses at the two closest recording sites. This value of corner tì.equency and the two values of seismic moment yield a Brune stress drop larger than 500 bars. However, a corner frequency value off; = 0.6 Hz and the seismic moment resulting from regional data allows the acceleration spectra to be reproduced on the entire available frequency band yielding to a Brune stress drop of 210 bars. The ambiguity on the corner frequency value associated to this earthquake is due to the limited frequency bandwidth available on the strong motion recordil1gs. Assuming the seismic moment estimated at regional distances from broad-band data, the moment magnitude for this earthquake is 5.7. The higher local magnitude (5.9) compared with the moment magnitude (5.7) is due to the weak regional attenuation. Beside this, site amplifications due to surface geology have produced the highest peak ground motions among those observed at the strong motion sites.

The corner frequencies and stress drops of intraplate earthquakes in the northeastern United States

1998 ◽  
Vol 88 (2) ◽  
pp. 531-542 ◽  
Author(s):  
Jinghua Shi ◽  
Won-Young Kim ◽  
Paul G. Richards
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Vertical Component ◽  
Corner Frequency ◽  
Northeastern United States ◽  
Empirical Green’S Function ◽  
Intraplate Earthquakes ◽  
Short Period ◽  
Empirical Green's Function ◽  
Stress Drops

Abstract This article presents the estimation of stress drops for small to middle-sized intraplate earthquakes in the northeastern United States. The vertical-component Sg and Lg waves of 49 earthquakes were analyzed, and their seismic corner frequencies and seismic moments were determined. For these events, both short-period and broadband records were obtained from stations in the region. There are eight events each of which has an aftershock good enough to be treated as its empirical Green's function, and their corner frequencies were estimated from empirical Green's function methods. For the other events, the corner frequencies were directly estimated by the spectral fitting of the vertical component of the Sg- or Lg-wave displacement spectrum with the ω-square source spectral model, using the available broadband and high-frequency short-period data and a frequency-dependent Q correction. The static stress drops, Δσ, were then calculated from the corner frequency and seismic moment. From our study, the source corner frequencies estimated by fitting the Lg displacement spectrum with the assumed ω-square source model are more consistent with the corner frequencies measured from empirical Green's function deconvolution method than those estimated from the intersection of horizontal low-frequency spectral asymptote and a line indicating the ω−2 decay above the corner frequency. The source corner frequencies we estimated proved to be most appropriate for the small to middle-sized earthquakes. The static stress drops calculated from these corner-frequency estimates tend to be independent of seismic moment for events above a certain size. For earthquakes with size less than about 2 × 1020 dyne-cm, the stress drop tends to decrease with decreasing moment, suggesting a breakdown in self-similarity below a threshold magnitude. A characteristic rupture size of about 100 m is implied for these smaller earthquakes.

Source parameters and scaling relationships of small earthquakes in the northeastern Caribbean

1981 ◽  
Vol 71 (4) ◽  
pp. 1173-1190
Author(s):  
Arthur Frankel
Keyword(s):  
Seismic Moment ◽  
Dynamic Stress ◽  
Source Parameters ◽  
Earthquake Swarm ◽  
Fold Increase ◽  
Virgin Islands ◽  
Scaling Relationships ◽  
Short Period ◽  
Relative Stress ◽  
Stress Drops

abstract The seismic moments and stress drops of 23 earthquakes (1.1 ≦ M ≦ 2.4) that occurred during an earthquake swarm in the Virgin Islands were determined from the analysis of their P waveforms. The data consist of digitally recorded seismograms collected by a short-period seismic network operating in the northeastern Caribbean. The events of the swarm are particularly useful for comparing the relative stress drops of small earthquakes, because their source to receiver paths and focal mechanisms are very similar. The static stress drops calculated for these earthquakes varied from about 0.2 to 2 bars. The data clearly illustrate that the static and dynamic stress drops of these earthquakes generally increased with the size (moment) of the events. The fault radii for these shocks increased with seismic moment, but only by a factor of 2 for a 100-fold increase in seismic moment. The velocity waveforms of the larger events were systematically more impulsive than those of the smaller earthquakes. These observations imply that, for this set of earthquakes, the final fault radius is a function of the stress drop that occurs during the rupture process.

Local Richter magnitude and total signal duration in southern California

1973 ◽  
Vol 63 (5) ◽  
pp. 1809-1827 ◽  
Author(s):  
Charles R. Real ◽  
Ta-Liang Teng
Keyword(s):  
Southern California ◽  
Epicentral Distance ◽  
Total Duration ◽  
Signal Duration ◽  
Local Magnitude ◽  
Total Signal ◽  
Source Effects ◽  
Short Period ◽  
Seismic Networks ◽  
Southern California Region

abstract Seismograms of 320 earthquakes (1,486 observations) from short-period seismometers occurring from January 1969 to April 1971 and 91 earthquakes (257 observations) during 1971 have been used to establish a relationship between total signal duration and the local Richter magnitude for the CIT and BHSN telemetered seismic networks in southern California. The data have been fitted using regression analysis to relationships of the form M τ = C 0 + C 1 log ⁡ τ + C 2 Δ M τ ≦ 3.8 M τ = C 0 + C 1 ( log ⁡ τ ) 2 + C 2 Δ M τ > 3.8 where τ is the total duration in seconds and Δ is the epicentral distance in kilometers. These relations explain up to 88 per cent (CIT) and 94 per cent (BHSN) of the variation in the data and yield magnitudes having standard deviations as low as 0.15 (CIT) and 0.14 (BHSN) magnitude units. It has been found that the local magnitude based on signal duration is relatively insensitive to variations in azimuth and source effects. In view of the limited distribution and low magnifiation of the Wood-Anderson torsion seismometer, and the previously recognized problems of “saturation” and instrument response associated with the amplitude technique, it is concluded that the method of duration applied to vertical short-period seismograph records will greatly improve the assignment of local magnitude to earthquakes in the southern California region.

Seismic noise characteristics in Chinese mainland

2020 ◽  
Author(s):  
Fang Wang ◽  
Weitao Wang ◽  
Jianfeng Long ◽  
Leiyu Mu
Keyword(s):  
Noise Level ◽  
Seismic Noise ◽  
Vertical Component ◽  
Chinese Mainland ◽  
Low Noise ◽  
Noise Characteristics ◽  
Power Spectral ◽  
Short Period ◽  
Power Spectral Densities ◽  
Noise Models

<p>Using the three-component continuous waveform recordings of 880 broadband seismic stations in China Seismic Network from January 2014 to December 2015, we calculated power spectral densities and probability density functions over the entire period for each station，and  investigated the characteristics of seismic noise in Chinese mainland. The deep analysis on the vertical recordings  indicates that the spatial distribution of noise levels is characterized by obvious zoning for different period bands.  Densely populated areas have higher short-period noise level than sparsely populated ones, suggesting that short-period noise is related to the intensity distribution of human activities such as transportation and industry. Meanwhile，the short-period noise level near the basin is higher than the mountainous areas，which is probably caused by the amplification effect of the sedimentary layer. The microseism energy  gradually decreases from the southeastern coastal lines to the inland regions. Furthermore, horizontal-component noise level  showed a striking constrast with the vertical component at microseismic and long-period bands. In consideration of  the zoning chracteristics and the need of seismic observations, high and low noise models were  acquired for each network , which were proved to be a more effective tool to identify locally abnormal signals including earthquake, instrumental error and various distrubance compared with the global new high and low model. </p>

Theoretical response of a seismograph at Yellowknife, Northwest Territories, to an underground explosion at the Nevada test site

1969 ◽  
Vol 6 (3) ◽  
pp. 517-520 ◽  
Author(s):  
H. S. Hasegawa ◽  
K. Whitham
Keyword(s):  
Northwest Territories ◽  
Vertical Component ◽  
Test Site ◽  
Underground Explosion ◽  
Nevada Test Site ◽  
Short Period

A comparison of the theoretical response of the short-period, vertical-component seismograph at Yellowknife to an underground explosion originating at the Nevada Test Site with a real seismogram indicates that the prime contributors to complexity are likely due to the following: (a) complex crustal reverberations at the N.T.S., (b) different phase arrivals, and (c) signal-generated noise at Yellow knife.

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