Estimates of magnitudes and short-period wave attenuation of Chinese earthquakes from Modified Mercalli intensity data

1984 ◽  
Vol 74 (3) ◽  
pp. 957-968
Author(s):  
Peishan Chen ◽  
Otto W. Nuttli
Keyword(s):  
Wave Attenuation ◽  
Body Wave ◽  
Empirical Relation ◽  
Historical Earthquakes ◽  
The Body ◽  
Intensity Data ◽  
Mountainous Regions ◽  
Short Period ◽  
Recent Earthquakes ◽  
Period Wave

Abstract Intensity data for Chinese earthquakes are used to estimate the body-wave magnitude, mb, of selected historical earthquakes and to estimate Q0, the 1-sec period Q value of Lg waves for various geographical areas of China. In order to derive the necessary empirical relation between the intensity distribution and mb, data are used from recent earthquakes, for which instrumentally obtained mb values as well as isoseismal maps are available. Average Qo values are approximately 175 for the mountainous regions of southwest China, 550 for southeastern China, and 150 for Taiwan. These values agree qualitatively with those obtained by Evernden (1983) and Chen et al. (1983), who utilized a different method of analysis of the intensity data

scholarly journals CodaNorm: A software package for the body-wave attenuation calculation by the coda-normalization method

SoftwareX ◽  
2017 ◽  
Vol 6 ◽  
pp. 30-35 ◽  
Author(s):  
Peter A. Predein ◽  
Anna A. Dobrynina ◽  
Tsyren A. Tubanov ◽  
Eugeny I. German
Keyword(s):  
Software Package ◽  
Wave Attenuation ◽  
Body Wave ◽  
Normalization Method ◽  
The Body ◽  
Coda Normalization Method ◽  
Coda Normalization

scholarly journals Inversion of the body waves from the Borrego Mountain earthquake to the source mechanism

1976 ◽  
Vol 66 (5) ◽  
pp. 1485-1499 ◽  
Author(s):  
L. J. Burdick ◽  
George R. Mellman
Keyword(s):  
Body Wave ◽  
High Stress ◽  
Time Function ◽  
The Body ◽  
Body Waves ◽  
Polarization Angle ◽  
Long Period ◽  
Amplitude Data ◽  
Short Period ◽  
Wide Range

abstract The generalized linear inverse technique has been adapted to the problem of determining an earthquake source model from body-wave data. The technique has been successfully applied to the Borrego Mountain earthquake of April 9, 1968. Synthetic seismograms computed from the resulting model match in close detail the first 25 sec of long-period seismograms from a wide range of azimuths. The main shock source-time function has been determined by a new simultaneous short period-long period deconvolution technique as well as by the inversion technique. The duration and shape of this time function indicate that most of the body-wave energy was radiated from a surface with effective radius of only 8 km. This is much smaller than the total surface rupture length or the length of the aftershock zone. Along with the moment determination of Mo = 11.2 ×1025 dyne-cm, this radius implies a high stress drop of about 96 bars. Evidence in the amplitude data indicates that the polarization angle of shear waves is very sensitive to lateral structure.

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.

scholarly journals Inferring the depth of pre-instrumental earthquakes from macroseismic intensity data: a case-history from Northern Italy

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Paola Sbarra ◽  
Pierfrancesco Burrato ◽  
Patrizia Tosi ◽  
Paola Vannoli ◽  
Valerio De Rubeis ◽  
...  
Keyword(s):  
Focal Depth ◽  
Historical Earthquakes ◽  
Northern Italy ◽  
Macroseismic Intensity ◽  
Intensity Data ◽  
Seismogenic Source ◽  
Seismogenic Faults ◽  
Intensity Field ◽  
Different Depths ◽  
Recent Earthquakes

Abstract Determining the hypocentral depth of pre-instrumental earthquakes is a long-standing geophysical issue that still awaits to be elucidated. Using very well documented recent earthquakes we found that the depth of crustal and upper-mantle events correlates well with the slope of the first 50 km of their intensity attenuation curve, regardless of their magnitude. We used this observation to build a magnitude-independent method for calculating the depth of selected historical and early-instrumental earthquakes of northern Italy based on their macroseismic intensity field. Our method relies on both standard intensity data and questionnaire-based data for 20 earthquakes, encompassing a relatively large range of magnitude (Mw 4.0–5.8) and depth (3.0–72.4 km), that occurred in Northern Italy between 1983 and 2019. We then used the method to estimate the depth of 20 older earthquakes that occurred in the same region between 1570 and 1972. Knowing the approximate depth of historical earthquakes is crucial for assigning them to the relevant seismogenic source, especially where seismogenic faults occur at different depths, allowing for a better characterisation of the region’s seismotectonic setting. Knowing the focal depth also allows recalculating the equivalent magnitude, which turns out to be consistently larger for deeper events, suggesting a reassessment of the local seismic hazard.

scholarly journals A harmonised instrumental earthquake catalogue for Iceland and the northern Mid-Atlantic Ridge

2021 ◽  
Vol 21 (7) ◽  
pp. 2197-2214
Author(s):  
Kristján Jónasson ◽  
Bjarni Bessason ◽  
Ásdís Helgadóttir ◽  
Páll Einarsson ◽  
Gunnar B. Guðmundsson ◽  
...  
Keyword(s):  
Body Wave ◽  
Historical Earthquakes ◽  
The Body ◽  
Plate Motion ◽  
Hazard Mapping ◽  
Local Data ◽  
Scientific Publications ◽  
Uncertainty Estimates ◽  
Completeness Magnitude ◽  
Mid Atlantic Ridge

Abstract. A comprehensive catalogue of historical earthquakes, with accurate epicentres and harmonised magnitudes is a crucial resource for seismic hazard mapping. Here we update and combine catalogues from several sources to compile a catalogue of earthquakes in and near Iceland, in the years 1900–2019. In particular the epicentres are based on local information, whereas the magnitudes are based on teleseismic observations, primarily from international online catalogues. The most reliable epicentre information comes from the catalogue of the Icelandic Meteorological Office, but this is complemented with information from several technical reports, scientific publications, and newspaper articles. The catalogue contains 1281 moment magnitude (Mw) ≥4 events, and the estimated completeness magnitude is Mw 5.5 in the first years, going down to Mw 4.5 for recent years. The largest magnitude is Mw 7.0. Such merging of local data and teleseismic catalogues has not been done before for Icelandic earthquakes, and the result is an earthquake map with much more accurate locations than earlier maps. The catalogue also lists 5640 additional earthquakes on the Mid-Atlantic Ridge, north of 43∘, with both epicentres and magnitudes determined teleseismically. When moment magnitudes are not available, proxy Mw values are computed using χ2 regression, normally on the surface-wave magnitude but exceptionally on the body-wave magnitude. Magnitudes of Mw≥4.5 have associated uncertainty estimates. The actual combined seismic moment released in the Icelandic earthquakes is found to be consistent with the moment estimated using a simple plate motion model, indicating that the seismic activity of the catalogue period might be typical of any 120-year time span. The catalogue is named ICEL-NMAR, and it is available online at http://data.mendeley.com (last access: 19 July 2021).

Identification of multiple underground explosions using the relative amplitude method

1988 ◽  
Vol 78 (2) ◽  
pp. 885-897
Author(s):  
R. A. Clark ◽  
R. G. Pearce
Keyword(s):  
Body Wave ◽  
The Body ◽  
P Wave ◽  
Relative Amplitude ◽  
Time Data ◽  
Large Measure ◽  
Source Discrimination ◽  
Nuclear Explosions ◽  
Short Period ◽  
Wave Forms

Abstract The relative amplitude method is applied to the few available good quality teleseismic P-wave seismograms from five presumed double nuclear explosions and one known multiple chemical explosion, under the “naive” assumption that the observed multiple arrivals correspond to P, pP, and sP from a single earthquake—an interpretation which is indeed consistent with the body-wave arrival time data in most cases. The purpose is to investigate the ability of relative amplitudes to identify correctly such multiple events for which established discrimination criteria may give earthquake-like or ambiguous results. For five of the examples, observed relative amplitudes from only four azimuthally well-distributed array seismograms are sufficient to exclude the single-earthquake interpretation. Deliberate attempts to simulate earthquake teleseismic P wave-forms using multiple explosions are restricted to simulation studies, and one of these is analyzed here using the same approach. We conclude that relative amplitudes can act as a valuable aid to source discrimination in cases where complexity gives rise to fallibility of conventional discriminants, even where only a small number of well-distributed teleseismic short-period array seismograms are available, their signal-to-noise ratios being maximized by suitable array design and careful choice of array site. The network need not be dense, since closely spaced observations of the focal sphere generally embody a large measure of redundancy.

On the relation between modified Mercalli intensity and body-wave magnitude

1979 ◽  
Vol 69 (3) ◽  
pp. 893-909
Author(s):  
Otto W. Nuttli ◽  
G. A. Bollinger ◽  
Donald W. Griffiths
Keyword(s):  
United States ◽  
South Carolina ◽  
San Francisco ◽  
Body Wave ◽  
Strong Motion ◽  
Historical Earthquakes ◽  
P Wave ◽  
Intensity Data ◽  
Lg Wave ◽  
Body Wave Magnitude

abstract This paper is concerned with estimating body-wave magnitude, mb, from the intensity distribution of an earthquake. Initially, it is assumed that modified Mercalli (MM) intensity values are directly related to the (A/T)z values of 1-Hz, Lg-wave ground motion. By comparison with the intensity values of a reference earthquake, magnitudes are calculated for 41 western and central United States earthquakes. Magnitudes of these earthquakes also are determined independently, in the conventional manner, using teleseismic P-wave amplitudes. Comparison of the two sets of magnitude values indicates that the assumed relation between 1-Hz, Lg-wave (A/T)z values and MM intensity does not hold exactly over the mb range of 4.0 to 6.2. An empirical equation is derived to adjust the mb values obtained from intensity data so that they agree with the teleseismic P-wave magnitudes. The method then is applied to estimate mb of some historical earthquakes which occurred prior to 1962. These include the set for which Kanamori and Jennings (1978) estimated ML from strong-motion accelerograms. Some noteworthy United States earthquakes also are considered. These include: the 1811 New Madrid earthquake for which mb is estimated to be 7.3; the 1886 Charleston, South Carolina earthquake, for which mb is estimated to be 6.6 to 6.9; the 1897 Giles County, Virginia earthquake, for which mb is estimated to be 5.8; the 1906 San Francisco, California earthquake, for which mb is estimated to be 6.8 to 7.1. The intensity-attenuation method cannot be used for estimating mb of all historical earthquakes because the intensity data are not always adequate. In some cases, however, the total felt area or the area enclosed by the Modified Mercalli IV isoseism can be determined. It was found that empirical equations relating mb to these areas, which were derived for central and northeastern United States earthquakes, also apply for events in the southeast. These empirical methods are used to estimate mb values for a set of historical Virginia earthquakes.

The identification and interpretation of upper mantle travel-time branches from measurements of dT/dΔ made on data recorded at the Yellowknife seismic array

1978 ◽  
Vol 15 (2) ◽  
pp. 227-236 ◽  
Author(s):  
A. Ram ◽  
R. F. Mereu ◽  
D. H. Weichert
Keyword(s):  
Travel Time ◽  
Upper Mantle ◽  
Body Wave ◽  
Processing Technique ◽  
The Body ◽  
Seismic Array ◽  
P Wave ◽  
Time Curve ◽  
Transition Zones ◽  
Short Period

There is broad agreement among various seismological studies that the upper mantle has two regions where very high positive velocity gradients or transition zones exist. In most cases, the presence of these zones implies that two major triplications are likely to exist in the body-wave travel-time curve for distances less than 30°. Because of the difficulties in observing and identifying later arrivals belonging to the various travel-time branches, the inversion of the seismic data is often very difficult. In this paper an adaptive processing technique was employed to examine the variations in slowness that occur along the first 36 s of the short-period P-wave trains recorded at the Yellowknife medium aperture seismic array. Over 100 earthquakes from the Alaska Peninsula and California regions were selected. From the California results we were able to clearly observe the 12–13 s/deg slowness branch as a later arrival out to distances as great as 26°. Other later arrival branches as well as cusps associated with the 400 and 650 km discontinuities were not well defined even though the cross-over point as determined from slowness measurements on first arrivals were clearly located. An inversion of the data showed that the '650 km' transition zone occurred at a much shallower depth west of the array compared to the corresponding region to the south.

The Mississippi Valley earthquakes of 1811 and 1812: Intesities, ground motion and magnitudes

1973 ◽  
Vol 63 (1) ◽  
pp. 227-248 ◽  
Author(s):  
Otto W. Nuttli
Keyword(s):  
North America ◽  
Ground Motion ◽  
Body Wave ◽  
Vertical Component ◽  
The Body ◽  
Eastern North America ◽  
Mississippi Valley ◽  
Isoseismal Map ◽  
Geological Conditions ◽  
Recent Earthquakes

abstract Contemporary newspaper accounts of the 1811-1812 Mississippi Valley earthquake sequence are used to construct a generalized isoseismal map of the first of three principal shocks of the sequence, that of December 16, 1811. The map is characterized by an unusually large felt area, with MM intensities of V as far away as the southeast Atlantic coastal area. By correlating the isoseismal map with that of recent earthquakes for which ground motion data are available, the body-wave magnitude of the December 16, 1811 earthquake is estimated to be 7.2. The other principal shocks, on January 23, 1812 and February 7, 1812, had estimated mb values of 7.1 and 7.4, respectively. The total energy released by the principal shocks and their larger-magnitude aftershocks is estimated to be equivalent to that of an mb = 7.5 (or Ms = 8.0) earthquake. The anomalously large areas of damage and of perceptibility of the principal shocks result from both the surficial geological conditions of the Mississippi Valley and the relatively low attenuation of surface-wave energy in eastern North America. Estimates of the vertical component of ground motion, for an earthquake of mb = 7.2 occurring in eastern North America, are given. These include values for particle velocity, displacement, and acceleration at frequencies of about 3, 1 and 0.3 Hz.

scholarly journals Wave Force Characteristics of Large-Sized Offshore Wind Support Structures to Sea Levels and Wave Conditions

2019 ◽  
Vol 9 (9) ◽  
pp. 1855
Author(s):  
Youn-Ju Jeong ◽  
Min-Su Park ◽  
Jeongsoo Kim ◽  
Sung-Hoon Song
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Wave Force ◽  
Diffraction Effect ◽  
Support Structures ◽  
Sea Levels ◽  
Irregular Wave ◽  
Long Period ◽  
Short Period ◽  
Period Wave

This paper presents the results of wave force tests conducted on three types of offshore support structures considering eight waves and three sea levels to investigate the corresponding wave forces. As a result of this study, it is found that the occurrence of shoaling in shallow water induces a significant increase of the wave force. Most of the test models at the shallow water undergo a nonlinear increase of the wave force with higher wave height increasing. In addition, the larger the diameter of the support structure within the range of this study, the larger the diffraction effect is, and the increase in wave force due to shoaling is suppressed. Under an irregular wave at the shallow water, the wave force to the long-period wave tends to be slightly higher than that of the short period wave since the higher wave height component included in the irregular wave has an influence on the shoaling. In addition, it is found that the influence of shoaling under irregular wave becomes more apparent in the long period.

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