Source dynamics of the Dasht-e Bayāz earthquake of August 31, 1968

1969 ◽  
Vol 59 (5) ◽  
pp. 1843-1861
Author(s):  
Mansour Niazi
Keyword(s):  
Stress Drop ◽  
Main Shock ◽  
Mean Value ◽  
The Body ◽  
P Wave ◽  
Polarization Angle ◽  
S Wave ◽  
Long Duration ◽  
First Motion ◽  
Complicated Pattern

abstract Radiation patterns of the P-wave first motion and S-wave polarization angle of the Dasht-e Bayāz earthquake of August 31, 1968, as well as its principal aftershock which occurred about 20 hours after the main shock are studied. The main shock data are consistent with the observed left-lateral strike-slip fault which accompanied it. The radiation pattern of the aftershock differs somewhat from that of the main shock and agrees with the directions of the secondary faulting in the area. Several lines of evidence pointing to a multiple source for the main shock are presented. They include complexity of the body phases, low value of the rupture speed as studied from the analysis of the surface wave spectra, reported long duration of shaking and complicated pattern of striations produced by faulting. Energy, moment and stress drop associated with the main shock are estimated. The resulting mean value of stress drop over the faulted surface has a range of 40-100 bars. Based on the age of some well-built structures in the area, it is proposed that no earthquake as severe as the recent one has occurred near the location of the August 31, 1968 earthquake during the last 800 years.

Fault parameters determined by near- and far-field data: The Wakasa Bay earthquake of March 26, 1963

1974 ◽  
Vol 64 (5) ◽  
pp. 1369-1382 ◽  
Author(s):  
Katsuyuki Abe
Keyword(s):  
Effective Stress ◽  
Stress Drop ◽  
P Wave ◽  
Slip Angle ◽  
Polarization Angle ◽  
S Wave ◽  
Seismological Data ◽  
Fault Parameters ◽  
Wakasa Bay ◽  
Dip Angle

Abstract The source process of the Wakasa Bay earthquake (M = 6.9, 35.80°N, 135.76°E, depth 4 km) which occurred near the west coast of Honshu Island, Japan, on March 26, 1963, is studied on the basis of the seismological data. Dynamic and static parameters of the faulting are determined by directly comparing synthetic seismograms with observed seismograms recorded at seismic near and far distances. The De Hoop-Haskell method is used for the synthesis. The average dislocation is determined to be 60 cm. The overall dislocation velocity is estimated to be 30 cm/sec, the rise time of the slip dislocation being determined as 2 sec. The other fault parameters determined, with supplementary data on the P-wave first motion, the S-wave polarization angle, and the aftershocks, are: source geometry, dip direction N 144°E, dip angle 68°, slip angle 22° (right-lateral strike-slip motion with some dip-slip component); fault dimension, 20 km length by 8 km width; rupture velocity, 2.3 km/sec (bilateral); seismic moment, 3.3 × 1025 dyne-cm; stress drop, 32 bars. The effective stress available to accelerate the fault motion is estimated to be about 40 bars. The approximate agreement between the effective stress and the stress drop suggests that most of the effective stress was released at the time of the earthquake.

The Fort Ross earthquake sequence, March and April, 1978

1979 ◽  
Vol 69 (6) ◽  
pp. 1841-1849
Author(s):  
Michael C. Stickney
Keyword(s):  
Main Shock ◽  
Vertical Movement ◽  
P Wave ◽  
S Wave ◽  
Motion Patterns ◽  
Arrival Times ◽  
Acoustic Reflection ◽  
San Andreas ◽  
First Motion ◽  
Plane Solution

abstract On March 31, 1978, an earthquake of coda magnitude 3.3 (ML = 3.7 BRK) occurred 5 km off the coast of northern California near Fort Ross. A single foreshock preceded the earthquake and approximately 60 aftershocks followed. Locations based on P- and S-wave arrival times indicate that the earthquakes occurred offshore, west of the San Andreas fault in the vicinity of a fault that is visible on acoustic reflection profiles. All earthquakes had hypocentral depths less than 8 km. A fault-plane solution from P-wave first motions suggests that the focal mechanism of the main shock consisted of nearly equal components of dextral and vertical movement on a plane striking northwest. Other events in this sequence had first-motion patterns strikingly different than the main shock, indicating that more than one type of faulting occurred during the sequence. Seismic moments computed for three aftershocks ranged from 3.8 × 1019 to 1.1 × 1019 dyne-cm.

scholarly journals Diagnostic Accuracy of the Electrocardiogram for Detection of Atrial and Ventricular Overloads in Dogs

2021 ◽  
Vol 49 ◽  
Author(s):  
Monique Machado Louredo Machado Louredo Teles Bombardelli ◽  
Tatiana Champion ◽  
Julio Cezar Juk Fischborn ◽  
Ana Bianca Ferreira Gusso
Keyword(s):  
Right Atrium ◽  
Wave Amplitude ◽  
Reference Value ◽  
Standard Test ◽  
The Body ◽  
P Wave ◽  
S Wave ◽  
Cardiac Chamber ◽  
Qrs Duration ◽  
The Right

Background: Analysis of the electrocardiogram may suggest atrial and ventricular overloads. However, it has a low sensitivity and specificity for diagnosis of cardiac chamber overload. The accuracy of electrocardiographic interpretation can be improve using new cut-offs for the duration and amplitude of the electrocardiographic waves. Our objective was to evaluate the use of the electrocardiogram in the diagnosis of atrial and ventricular overload, using echocardiography as the gold standard test for the diagnosis of atrioventricular overload. We aimed to define new cut-off values that would increase the sensitivity and specificity of the electrocardiogram for diagnosis of chamber overload in dogs.Materials, Methods & Results: Eletrocardiogram records were obtained in 81 dogs divided into 3 groups: Group 1A (healthy dogs 10 kg); Group 1B (dogs 10 kg with mitral or tricuspid valve disease); Group 2 (dogs weighing between 10.1 and 20 kg) and Group 3 (dogs > 20.1 kg). Duration in milliseconds (ms) and amplitude in millivolts (mV) of P waves and QRS complexes, PR and QT segment, T wave amplitude and ST segment were evaluated in lead DII. Using leads I and III, the mean cardiac electrical axis in the frontal plane, expressed in degrees, was determined as the mean of three consecutive measurements. For Group 1A and 1B the duration of P wave was < 45 ms and QRS duration < 55 ms. In Group 2 the duration of P wave was < 47 ms and QRS duration < 57 ms. In Group 3 the duration of P wave was < 50 ms and duration QRS < 64 ms. These values (duration of P wave and QRS duration) were compared with echocardiographic measurements of the left atrium, considering the reference value AE/Ao < 1.4 and measurements of the left ventricle in M-mode according to the body weight, respectively. A P wave amplitude < 0.4 mV suggested that the right atrium size was normal and this was compared with the area of the right atrium measured on the echocardiogram. The right ventricle was assessed using the amplitude of S wave and right axis deviation and compared with the right ventricular area obtained by echocardiography. The reference value of the right atrium and right ventricle is according to the body weight. For both the right and left atria, there was concordance between the diagnoses with electrocardiography and echocardiography. For the right and left ventricle was no agreement between the diagnoses. All criteria examined had low sensitivities, usually with high specificities. But it was not possible to determine a new cut-off that would improve the sensitivity of the electrocardiogram for diagnosis of atrial and ventricular overload in dogs. Discussion: The electrocardiogram analysis produced false interpretations for the measures indicative of atrioventricular overloads and should not be used alone, for diagnosis of cardiac chamber overload. The standard electrocardiographic reference values, for P wave duration and amplitude, were excellent for identification of normal atrial size. However, QRS duration, R wave amplitude (dependent of the dog’s weight) and S wave amplitude, associated with cardiac electrical axis cannot be used for diagnosis of ventricle overload. Electrocardiographic analysis should not be used as a tool to assess cardiac chamber overload, which should be diagnosed by echocardiography and clinical investigation. Based on our findings echocardiogram is the gold standard test indicated to identify overload of cardiac chambers.

Combination of P and S data for the determination of earthquake focal mechanism

1971 ◽  
Vol 61 (6) ◽  
pp. 1655-1673 ◽  
Author(s):  
Umesh Chandra
Keyword(s):  
Focal Mechanism ◽  
P Wave ◽  
Wave Polarization ◽  
S Wave ◽  
Polarization Data ◽  
Wave Data ◽  
Earthquake Focal Mechanism ◽  
First Motion ◽  
Depth Ranges

abstract A method has been proposed for the combination of P-wave first-motion directions and S-wave polarization data for the numerical determination of earthquake focal mechanism. The method takes into account the influence of nearness of stations with inconsistent P-wave polarity observations, with respect to the assumed nodal planes. The mechanism solutions for six earthquakes selected from different geographic locations and depth ranges have been determined. Equal area projections of the nodal planes together with the P-wave first-motion and S-wave polarization data are presented for each earthquake. The quality of resolution of nodal plane determination on the basis of P-wave data, S-wave polarization, and the combination of P and S-wave data according to the present method, is discussed.

The Broach earthquake of March 23, 1970

1972 ◽  
Vol 62 (1) ◽  
pp. 47-61
Author(s):  
Harsh K. Gupta ◽  
Indra Mohan ◽  
Hari Narain
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
Geological Structure ◽  
P Wave ◽  
Field Observations ◽  
B Values ◽  
Macroseismic Effects ◽  
Godavari Valley ◽  
First Motion ◽  
Largest Aftershock

Abstract The recent seismicity of the Broach region has been studied and correlated with the regional geological structure. The macroseismic effects are briefly described. Analysis of the first motion of P-wave data indicates the plane striking N 92°E to be the fault plane as supported by field observations also. The present seismic activity is found to be similar to the recent Godavari Valley earthquake sequence of April 1970 and different from the earthquakes in the Koyna region on the basis of b values, foreshock-aftershock pattern, and the ratio of the largest aftershock to the main shock magnitude.

The partition of radiated energy between P and S waves

1984 ◽  
Vol 74 (2) ◽  
pp. 361-376
Author(s):  
John Boatwright ◽  
Jon B. Fletcher
Keyword(s):  
Wave Energy ◽  
Body Wave ◽  
Focal Mechanisms ◽  
The Body ◽  
Body Waves ◽  
P Wave ◽  
Corner Frequency ◽  
S Wave ◽  
S Waves ◽  
Radiated Energy

Abstract Seventy-three digitally recorded body waves from nine multiply recorded small earthquakes in Monticello, South Carolina, are analyzed to estimate the energy radiated in P and S waves. Assuming Qα = Qβ = 300, the body-wave spectra are corrected for attenuation in the frequency domain, and the velocity power spectra are integrated over frequency to estimate the radiated energy flux. Focal mechanisms determined for the events by fitting the observed displacement pulse areas are used to correct for the radiation patterns. Averaging the results from the nine events gives 27.3 ± 3.3 for the ratio of the S-wave energy to the P-wave energy using 0.5 〈Fi〉 as a lower bound for the radiation pattern corrections, and 23.7 ± 3.0 using no correction for the focal mechanisms. The average shift between the P-wave corner frequency and the S-wave corner frequency, 1.24 ± 0.22, gives the ratio 13.7 ± 7.3. The substantially higher values obtained from the integral technique implies that the P waves in this data set are depleted in energy relative to the S waves. Cursory inspection of the body-wave arrivals suggests that this enervation results from an anomalous site response at two of the stations. Using the ratio of the P-wave moments to the S-wave moments to correct the two integral estimates gives 16.7 and 14.4 for the ratio of the S-wave energy to the P-wave energy.

Focal mechanism of the Prince William Sound, Alaska earthquake of March 28, 1964

1969 ◽  
Vol 59 (2) ◽  
pp. 799-811
Author(s):  
Samuel T. Harding ◽  
S. T. Algermissen
Keyword(s):  
Focal Mechanism ◽  
P Wave ◽  
Type I ◽  
Type Ii ◽  
Prince William Sound ◽  
Wave Polarization ◽  
S Wave ◽  
Polarization Data ◽  
Wave Data ◽  
First Motion

abstract Two nodal planes for P were determined using a combination of P-wave first motion and S-wave polarization data and from S-wave data alone. The S-wave polarization error, δ∈, is slightly lower for a type Il than for a type I mechanism. The type I mechanism solution indicates a predominately dip-slip faulting on a steeply dipping plane. The preferred solution is a type II mechanism with the following P nodal planes: strike N62°E, dip 82°S, (a plane); strike N22°W, dip 52°W, (b plane). Two solutions are possible: right lateral faulting which strikes northeast; or, left lateral faulting which strikes northwest. Both possible fault planes dip steeply.

Source mechanism and surface-wave attenuation studies for Tibet earthquake of July 14, 1973

1979 ◽  
Vol 69 (3) ◽  
pp. 737-750
Author(s):  
D. D. Singh ◽  
Harsh K. Gupta
Keyword(s):  
Surface Wave ◽  
Stress Drop ◽  
Wave Attenuation ◽  
Source Parameters ◽  
High Stress ◽  
The Body ◽  
P Wave ◽  
Slip Angle ◽  
Apparent Stress ◽  
Crust And Upper Mantle

abstract Focal mechanism for Tibet earthquake of July 14, 1973 (M = 6.9, mb = 6.0) has been determined using the P-wave first motions, S-wave polarization angles, and surface-wave spectral data. A normal faulting is obtained with a plane having strike N3°W, dip 51°W, and slip angle 81°. The source parameters have been estimated for this event using the body- and surface-wave spectra. The seismic moment, fault length, apparent stress, stress drop, seismic energy release, average dislocation, and fault area are estimated to be 2.96 × 1026 dyne-cm, 27.4 km, 14 bars, 51 bars, 1.4 × 1022 ergs, 157 cm, and 628 km2, respectively. The high stress drop and apparent stress associated with this earthquake indicate that the high stresses are prevailing in this region. The specific quality factor Q is found to vary from 21 to 1162 and 22 to 1110 for Rayleigh and Love waves, respectively. These wide ranges of variation in the attenuation data may be due to the presence of heterogeneity in the crust and upper mantle.

scholarly journals Comparison of recent S-wave indicating methods

2018 ◽  
Vol 29 ◽  
pp. 00019
Author(s):  
Katarzyna Hubicka ◽  
Jakub Sokolowski
Keyword(s):  
Real Data ◽  
The Body ◽  
Body Waves ◽  
Identification Accuracy ◽  
P Wave ◽  
S Wave ◽  
P Waves ◽  
S Waves ◽  
Mode Decomposition ◽  
Wave Arrival

Seismic event consists of surface waves and body waves. Due to the fact that the body waves are faster (P-waves) and more energetic (S-waves) in literature the problem of their analysis is taken more often. The most universal information that is received from the recorded wave is its moment of arrival. When this information is obtained from at least four seismometers in different locations, the epicentre of the particular event can be estimated [1]. Since the recorded body waves may overlap in signal, the problem of wave onset moment is considered more often for faster P-wave than S-wave. This however does not mean that the issue of S-wave arrival time is not taken at all. As the process of manual picking is time-consuming, methods of automatic detection are recommended (these however may be less accurate). In this paper four recently developed methods estimating S-wave arrival are compared: the method operating on empirical mode decomposition and Teager-Kaiser operator [2], the modification of STA/LTA algorithm [3], the method using a nearest neighbour-based approach [4] and the algorithm operating on characteristic of signals’ second moments. The methods will be also compared to wellknown algorithm based on the autoregressive model [5]. The algorithms will be tested in terms of their S-wave arrival identification accuracy on real data originating from International Research Institutions for Seismology (IRIS) database.

scholarly journals Determination of rupture duration and stress drop for earthquakes in southern California

1983 ◽  
Vol 73 (6A) ◽  
pp. 1527-1551
Author(s):  
Arthur Frankel ◽  
Hiroo Kanamori
Keyword(s):  
Stress Drop ◽  
Pulse Width ◽  
Southern California ◽  
Main Shock ◽  
P Wave ◽  
Fault System ◽  
Zero Crossing ◽  
Main Shocks ◽  
Seismic Networks ◽  
Rupture Duration

Abstract A simple technique is developed for determining the rupture duration and stress drop of earthquakes between magnitudes 3.5 and 4.0 using the time between the P-wave onset and the first zero crossing (τ1/2) on seismograms from local seismic networks. This method is applied to 10 main shocks in southern California to investigate regional variations in stress drop. The initial pulse widths of 65 foreshocks or aftershocks of these events were measured. Values of τ1/2 for small earthquakes below about magnitude 2.2 are generally observed to remain constant with decreasing magnitude in four sequences studied. The relative pulse width of a particular main shock (M ≧ 3.5) at a given station is found to be correlated with the relative pulse width of its aftershocks recorded at that station. These observations are interpreted to signify that the waveforms of these small events (M ≦ 2.2) are essentially the impulse response of the path between the source and receiver. Values of τ1/2 determined from small foreshocks and aftershocks are, therefore, subtracted (in effect deconvolved) from those of each main shock to obtain an estimate of the rupture duration of the main shock which is corrected for path effects. Significant variations in rupture duration and stress drop are observed for the main shocks studied. Aftershock locations and azimuthal variations in τ1/2 both indicate that the rupture zone of one earthquake expanded unilaterally. A factor of 10 variation in stress drop is calculated for two adjacent events of similar seismic moments occurring 1 hr apart on the San Jacinto fault system. The first event in this pair had the highest stress drop of the events studied (860 bars) and was followed within 8 months by a magnitude 5.5 earthquake 2 km away.

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