The body-wave magnitude of the great 1857 California earthquake

1979 ◽  
Vol 69 (6) ◽  
pp. 2117-2119
Author(s):  
Otto W. Nuttli
Keyword(s):  
Body Wave ◽  
The Body ◽  
Body Wave Magnitude

Seismic source functions and magnitude determinations for underground nuclear detonations

1977 ◽  
Vol 67 (1) ◽  
pp. 135-158
Author(s):  
John R. Murphy
Keyword(s):  
Body Wave ◽  
Broad Band ◽  
Seismic Source ◽  
Source Model ◽  
The Body ◽  
P Wave ◽  
Cube Root ◽  
Motion Data ◽  
Surface Wave Data ◽  
Body Wave Magnitude

abstract A variety of near-regional, regional, and teleseismic ground-motion data have been used to evaluate proposed models of the nuclear seismic source function for underground detonations in tuff/rhyolite emplacement media. It has been found that both the near-regional broad-band seismic data and the teleseismic body-wave magnitude data are consistent with the modified source model proposed by Mueller and Murphy (1971) but not with the simple cube-root of the yield-scaling source model. In particular, the observed linearity and slopes of the body-wave magnitude-yield curves as well as the observed variation of P-wave period with yield have been found to be fully compatible with the modified source model. On the other hand, it has been concluded that the observed long-period surface-wave data are inconsistent with a simple, spherically symmetric source model. The results of a preliminary analysis have suggested that this discrepancy may be related to the spall closure phenomenon.

Precision of different varieties of magnitude

1972 ◽  
Vol 62 (3) ◽  
pp. 789-792
Author(s):  
B. F. Howell
Keyword(s):  
Surface Wave ◽  
Frequency Band ◽  
Wave Amplitude ◽  
Body Wave ◽  
The Body ◽  
Surface Wave Magnitude ◽  
Lower Standard ◽  
Standard Deviations ◽  
Body Wave Magnitude

Abstract The standard deviations of the body-wave magnitude, surface-wave magnitude and frequency-band magnitude of four shallow (H < 60 km) earthquakes are compared. For three out of four of these earthquakes, surface-wave magnitude exhibited lower standard deviations than either body-wave or frequency-band magnitude. In three out of the four cases, lower standard deviations were obtained by calculating surface-wave magnitude from the largest surface-wave amplitude than from time-correlated surface-wave phases.

scholarly journals Seismological investigation of the 2016 January 6 North Korean underground nuclear test

2016 ◽  
Vol 206 (3) ◽  
pp. 1487-1491 ◽  
Author(s):  
Lian-Feng Zhao ◽  
Xiao-Bi Xie ◽  
Wei-Min Wang ◽  
Jin-Lai Hao ◽  
Zhen-Xing Yao
Keyword(s):  
Body Wave ◽  
Broad Band ◽  
Test Site ◽  
Nuclear Test ◽  
The Body ◽  
The North ◽  
Nuclear Tests ◽  
Master Event ◽  
Fully Coupled ◽  
Body Wave Magnitude

Abstract Seismology plays an important role in characterizing potential underground nuclear tests. Using broad-band digital seismic data from Northeast China, South Korea and Japan, we investigated the properties of the recent seismic event occurred in North Korea on 2016 January 6. Using a relative location method and choosing the previous 2006 explosion as the master event, the 2016 event was located within the North Korean nuclear test site, with its epicentre at latitude 41.3003°N and longitude 129.0678°E, approximately 900 m north and 500 m west of the previous event on 2013 February 12. Based on the error ellipse, the relocation uncertainty was approximately 70 m. Using the P/S spectral ratios, including Pg/Lg, Pn/Lg and Pn/Sn, as the discriminants, we identify the 2016 event as an explosion rather than an earthquake. The body-wave magnitude calculated from regional wave Lg is mb(Lg) equal to 4.7 ± 0.2. Adopting an empirical magnitude–yield relation, and assuming that the explosion is fully coupled and detonated at a normally scaled depth, we find that the seismic yield is about 4 kt, with the uncertainties allowing a range from 2 to 8 kt.

The body-wave magnitude mb: an attempt to rationalize the distance-depth correction q(Δ, h)

2020 ◽  
Vol 223 (1) ◽  
pp. 270-288
Author(s):  
Nooshin Saloor ◽  
Emile A Okal
Keyword(s):  
Large Scale ◽  
Body Wave ◽  
Exact Algorithm ◽  
Large Data ◽  
The Body ◽  
P Wave ◽  
Small Scale ◽  
Data Sets ◽  
Data Set ◽  
Body Wave Magnitude

SUMMARY We explore the possible theoretical origin of the distance–depth correction q(Δ, h) introduced 75 yr ago by B. Gutenberg for the computation of the body-wave magnitude mb, and still in use today. We synthesize a large data set of seismograms using a modern model of P-wave velocity and attenuation, and process them through the exact algorithm mandated under present-day seismological practice, to build our own version, qSO, of the correction, and compare it to the original ones, q45 and q56, proposed by B. Gutenberg and C.F. Richter. While we can reproduce some of the large scale variations in their corrections, we cannot understand their small scale details. We discuss a number of possible sources of bias in the data sets used at the time, and suggest the need for a complete revision of existing mb catalogues.

Focal mechanism and source depth of earthquakes from body- and surface-wave data

1971 ◽  
Vol 61 (5) ◽  
pp. 1369-1379 ◽  
Author(s):  
Nezihi Canitez ◽  
M. Nafi Toksöz
Keyword(s):  
Surface Wave ◽  
Body Wave ◽  
Source Parameters ◽  
Focal Depth ◽  
Spectral Ratio ◽  
The Body ◽  
Spectral Ratios ◽  
Motion Data ◽  
Wave Data ◽  
Surface Wave Data

abstract The determination of focal depth and other source parameters by the use of first-motion data and surface-wave spectra is investigated. It is shown that the spectral ratio of Love to Rayleigh waves (L/R) is sensitive to all source parameters. The azimuthal variation of the L/R spectral ratios can be used to check the fault-plane solution as well as for focal depth determinations. Medium response, attenuation, and source finiteness seriously affect the absolute spectra and introduce uncertainty into the focal depth determinations. These effects are nearly canceled out when L/R amplitude ratios are used. Thus, the preferred procedure for source mechanism studies of shallow earthquakes is to use jointly the body-wave data, absolute spectra of surface waves, and the Love/Rayleigh spectral ratios. With this procedure, focal depths can be determined to an accuracy of a few kilometers.

Preliminary body-wave analysis of the St. Elias, Alaska earthquake of February 28, 1979

1980 ◽  
Vol 70 (2) ◽  
pp. 419-436
Author(s):  
John Boatwright
Keyword(s):  
New York ◽  
Body Wave ◽  
The Body ◽  
Rupture Velocity ◽  
Wave Analysis ◽  
S Waves ◽  
Initial Event ◽  
Whole Space ◽  
A New Technique ◽  
Alaska Earthquake

abstract Employing a new technique for the body-wave analysis of shallow-focus earthquakes, we have made a preliminary analysis of the St. Elias, Alaska earthquake of February 28, 1979, using five long-period P and S waves recorded at three WWSSN stations and at Palisades, New York. Using a well determined focal mechanism and an average source depth of ≈ 11 km, the interference of the depth phases (i.e., pP and sP, or sS) has been deconvolved from the recorded pulse shapes to obtain velocity and displacement pulse shapes as they would appear if the earthquake had occurred within an infinite medium. These “approximate whole space” pulse shapes indicate that the rupture contained three distinct subevents as well as a small initial event which preceded this subevent sequence by about 7 sec. From the pulse rise times of the subevents, their rupture lengths are estimated as 12, 27, and 17 km, assuming that the subevent rupture velocity was 3 km/sec. Overall, the earthquake ruptured ≈ 60 km to the southeast with an average rupture velocity of 2.2 km/sec. The cumulative body-wave moment for the whole event, 1.2 × 1027 dyne-cm, is substantially smaller than the surface-wave moments reported by Lahr et al. (1979) of 5 × 1027 dyne-cm. The moments of the subevents are estimated to be 0.6, 3.2, and 7.5 × 1026 dyne-cm, respectively.

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