scholarly journals Amplitude-distance curves of P, S and L waves in Central Balkans for short and medium period seismographs

1994 ◽  
Vol 37 (3) ◽  
Author(s):  
L. Christoskov
Keyword(s):  
Surface Wave ◽  
Magnitude Scale ◽  
Surface Wave Magnitude ◽  
Basic Principles ◽  
Balkan Region

The basic principles for deriving the amplitude-distance curves or calibrating functions at short epicentral distances for the central part of the Balkan region are described. A procedure for unification of magnitude determinations for P, S and L waves is applied on the basis of the teleseismic surface wave magnitude scale. The results for short and medium period seismographs are presented.

scholarly journals Magnitudes of great shallow earthquakes from 1904 to 1952

1977 ◽  
Vol 67 (3) ◽  
pp. 587-598 ◽  
Author(s):  
Robert J. Geller ◽  
Hiroo Kanamori
Keyword(s):  
Surface Wave ◽  
Seismic Moment ◽  
Body Wave ◽  
Magnitude Scale ◽  
Surface Wave Magnitude ◽  
Class A ◽  
The Earth ◽  
Shallow Earthquakes ◽  
The Moment

abstract The “revised magnitudes”, M, converted from Gutenberg's unified magnitude, m, and listed by Richter (1958) and Duda (1965) are systematically higher than the magnitudes listed by Gutenberg and Richter (1954) in Seismicity of the Earth. This difference is examined on the basis of Gutenberg and Richter's unpublished original worksheets for Seismicity of the Earth. It is concluded that (1) the magnitudes of most shallow “class a” earthquakes in Seismicity of the Earth are essentially equivalent to the 20-sec surface-wave magnitude, Ms; (2) the revised magnitudes, M, of most great shallow (less than 40 km) earthquakes listed in Richter (1958) (also used in Duda, 1965) heavily emphasize body-wave magnitudes, mb, and are given by M=14Ms+34(1.59mb−3.97). For earthquakes at depths of 40 to 60 km, M is given by M = (1.59 mb − 3.97). M and Ms are thus distinct and should not be confused. Because of the saturation of the surface-wave magnitude scale at Ms ≃ 8.0, use of empirical moment versus magnitude relations for estimating the seismic moment results in large errors. Use of the fault area, S, is suggested for estimating the moment.

The 1904 Ms6.8 Mw7.0-7.2 Cape Turnagain, New Zealand, earthquake

2006 ◽  
Vol 39 (4) ◽  
pp. 183-207
Author(s):  
G. L. Downes
Keyword(s):  
New Zealand ◽  
Surface Wave ◽  
Seismic Hazard ◽  
Goodness Of Fit ◽  
Central Business District ◽  
Maximum Magnitude ◽  
Surface Wave Magnitude ◽  
Plate Interface ◽  
Attenuation Relations ◽  
Instrumental Records

The 1904 August 09 NZT (August 08 UT) MS6.8 earthquake caused widespread structural and chimney damage from Napier to Wellington and was felt over a large part of New Zealand. Other than a brief paper in 1905, and determinations of its surface wave magnitude in the last 20 years, little has been done to better locate the earthquake or detail its effects. Comprehensive data have now been obtained from searches of historical documents, including newspapers, private and government papers, as well as instrumental records. Interpretation of the intensity data shows that the earthquake was probably centred near Cape Turnagain at relatively shallow depth. The paucity of aftershocks suggests that the earthquake occurred either on the subduction interface, or in the lower seismicity band or upper mantle of the subducting Pacific Plate. The area encompassed by the higher intensity isoseismals suggests the earthquake had a magnitude greater than the calculated surface wave magnitude MS6.75 ± 0.14 — possibly as high as MW7.2. At this magnitude, the earthquake becomes a more significant event in New Zealand’s historical record, and certainly the largest earthquake suspected of rupturing the plate interface along the Hikurangi Margin. A notable feature of the earthquake is the chimney and parapet damage caused in parts of Wellington Central Business District, approximately 170 km from the epicentre. Much of the city and inner suburbs experienced MM5-6, while MM6-7 occurred in several areas, mostly in those areas that are recognised as possibly susceptible to shaking enhancement, but also in several locations outside these areas. The 1904 Cape Turnagain earthquake has several implications for seismic hazard dependent on whether it was intra-slab or on the plate interface. Of particular importance, are the questions whether the damage in Wellington is exceptional and could represent microzone, focussing or directivity effects; the goodness of fit of the intensity distribution to modelled isoseismals using published attenuation relations; the compatibility of the magnitude with the maximum magnitude/magnitude cut-offs used in this area in the New Zealand Probabilistic Seismic Hazard model; and finally, the possibility that the 1904 earthquake might characterise plate interface earthquakes in southern Hawke’s Bay.

scholarly journals Brief report on the January 17 1994 Northridge earthquake in Los Angeles

1994 ◽  
Vol 27 (1) ◽  
pp. 55-75
Author(s):  
Editor
Keyword(s):  
Surface Wave ◽  
Los Angeles ◽  
Press Release ◽  
Northridge Earthquake ◽  
Local Magnitude ◽  
Surface Wave Magnitude ◽  
Detailed Report ◽  
Information Centre ◽  
Standard Time ◽  
San Fernando

An earthquake struck the San Fernando Valley on January 17 at 4:30 am. Pacific Standard Time. The epicenter was located at 34°13' North, 118°3' West at a depth of 14.6km. The surface wave magnitude from the National Earthquake Information Centre was 6.6. The local magnitude was 6.4. Most of this information was prepared within a few days of the earthquake occurring and some of the material included in this report was issued as a press release. A more detailed report is currently being prepared by the Reconnaissance Team sent by the Society.

Comparison of two surface-wave magnitude scales: M of Gutenberg and Richter (1954) and MS of “Preliminary determination of epicenters”

1984 ◽  
Vol 74 (6) ◽  
pp. 2357-2378
Author(s):  
J. J. Lienkaemper
Keyword(s):  
Standard Deviation ◽  
Surface Wave ◽  
Ad Hoc ◽  
Surface Wave Magnitude ◽  
Single Station ◽  
Magnitude Scales ◽  
The Mean ◽  
Probabilistic Criteria ◽  
Preliminary Determination

Abstract The Prague formula (Vanek et al., 1962), which is used for Preliminary Determination of Epicenters (PDE) magnitudes, exceeds that of Gutenberg (1945) by 0.19 unit of MS, leading to the false assumption that mean MS of PDE are inherently 0.19 larger than Gutenberg and Richter (1954) magnitudes, MGR. Recomputation of MS using Gutenberg's methods and Gutenberg-Richter (G-R) notepad data shows that MS values in the G-R notepads are ∼0.1 unit of MS too large on average, while MGR values are 0.05 larger still. Total inflation of MGR over recomputed MS values is 0.16 on average. MS for the same events recomputed with the Prague formula are thus only 0.03 unit of MS higher on average than MGR. Thus, PDE values of MS are on average directly comparable to MGR. This relationship probably is a consequence of the Prague formula having been calibrated to Gutenberg's revised magnitudes and MGR values. Surface-wave magnitude residuals summed over many events appear to fit a normal Gaussian distribution with a standard deviation of 0.28 unit-of-MS for two large independent samples. Thus, anomalous single-station MS values can be excluded from averaging, using probabilistic criteria rather than the ad hoc criteria used currently, and standard deviations of MS from the mean are valid estimates of error.

Surface-wave constraints on the August 1, 1975, Oroville earthquake

1977 ◽  
Vol 67 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Robert S. Hart ◽  
Rhett Butler ◽  
Hiroo Kanamori
Keyword(s):  
Surface Wave ◽  
Rayleigh Waves ◽  
Body Wave ◽  
Source Parameters ◽  
The Body ◽  
Wave Radiation ◽  
Spectral Amplitude ◽  
Surface Wave Magnitude ◽  
Long Period ◽  
Short Period

abstract Observations of Love and Rayleigh waves on WWSSN and Canadian Network seismograms have been used to place constraints upon the source parameters of the August 1, 1975, Oroville earthquake. The 20-sec surface-wave magnitude is 5.6. The surface-wave radiation pattern is consistent with the fault geometry determined by the body-wave study of Langston and Butler (1976). The seismic moment of this event was determined to be 1.9 × 1025 dyne-cm by both time-domain and long-period (T ≥ 50 sec) spectral amplitude determinations. This moment value is significantly greater than that determined by short-period studies. This difference, together with the low seismic efficiency of this earthquake, indicates that the character of the source is intrinsically different at long periods from those aspects which dominate the shorter-period spectrum.

A Discussion on the measurement and interpretation of changes of strain in the Earth - Quartz fibre accelerometers

1973 ◽  
Vol 274 (1239) ◽  
pp. 231-243 ◽  
Keyword(s):  
Surface Wave ◽  
Free Oscillation ◽  
Signal To Noise Ratio ◽  
Detection Threshold ◽  
Vertical Displacement ◽  
Differential Capacitance ◽  
Surface Wave Magnitude ◽  
Quartz Fibre ◽  
San Fernando ◽  
Seismic Accelerations

New vertical and horizontal accelerometers based on torsion fibres of fused quartz and differential capacitance position sensors are discussed. The instruments have low drift, flat response from d.c. to nearly 1 Hz, and gain sufficient to measure tidal and seismic accelerations. They are small, weigh less than 9 kg, and have strict control of internal temperature and pressure. Tidal, free oscillation, and seismic data from the accelerometers are presented. Records of earthquakes of surface wave magnitude 6.5 to 7.5 yield free oscillation spectra with greater than 20 dB signal-to-noise ratio. Records of distant teleseisms provide a detection threshold of surface wave magnitude 2.5 at a distance of 30°. A record of the San Fernando earthquake of February 1971 gives an upper bound of 1mm for a vertical displacement step 190 km from the source.

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