The S wave project for focal mechanism studies earthquakes of 1962

1964 ◽  
Vol 54 (6B) ◽  
pp. 2199-2208 ◽  
Author(s):  
William Stauder ◽  
G. A. Bollinger
Keyword(s):  
Focal Mechanism ◽  
P Wave ◽  
S Wave ◽  
Polarization Data ◽  
Saint Louis ◽  
Saint Louis University ◽  
S Waves ◽  
Focal Mechanism Solutions ◽  
First Motion

Abstract The Department of Geophysics of Saint Louis University has instituted a routine program for the determination of the focal mechanism of the larger earthquakes of each year using methods developed for the use of S waves in focal mechanism studies. Suites of records from selected stations are assembled from the WWSS microfilm file for each earthquake of interest. A combination of P-wave first motion and S-wave polarization data is then used to determine graphically the mechanism of the earthquakes. Thirty-six earthquakes of 1962 were selected for study. The focal mechanism solutions are presented for twenty-three of these shocks. There is evidence of patterns characteristic of the focal mechanism of earthquakes occurring in Kamchatka, the Aleutian Islands and South America. A complete presentation of all the data and of all the solutions is available in a more lengthy report.

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.

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.

S waves: Alaska and other earthquakes

1960 ◽  
Vol 50 (4) ◽  
pp. 581-597 ◽  
Author(s):  
William Stauder
Keyword(s):  
Focal Mechanism ◽  
Fault Plane ◽  
P Wave ◽  
Wave Analysis ◽  
Point Model ◽  
S Wave ◽  
S Waves ◽  
Wave Solutions ◽  
Single Force

ABSTRACT Techniques of S wave analysis are used to investigate the focal mechanism of four earthquakes. In all cases the results of the S wave analysis agree with previously determined P wave solutions and conform to a dipole with moment or single couple as the point model of the focus. Further, the data from S waves select one of the two nodal planes of P as the fault plane. Small errors in the determination of the angle of polarization of S are shown to result in scatter in the data of a peculiar character which might lead to misinterpretation. The same methods of analysis which in the present instances show excellent agreement with a dipole with moment source are the methods which in a previous paper required a single force type mechanism for a different group of earthquakes.

Stationary phase approximation in focal mechanism determination

1970 ◽  
Vol 60 (4) ◽  
pp. 1221-1229
Author(s):  
Umesh Chandra
Keyword(s):  
Stationary Phase ◽  
Wave Spectrum ◽  
P Wave ◽  
Phase Approximation ◽  
Wave Polarization ◽  
S Wave ◽  
Polarization Data ◽  
P Waves ◽  
Depth Ranges

abstract Tests of the stationary phase approximation method applied to P waves for the determination of focal mechanisms have been carried through for eight earthquakes selected from different geographic locations and depth ranges. The results are found to be in close agreement with the solutions obtained from S-wave polarization data for four earthquakes and in reasonable agreement for three earthquakes. In general, however, the P polarities are more consistent with S-wave polarization solutions than with the solutions obtained by the present method. The stationary phase solutions agree with the P-wave spectrum solutions determined in a previous study. The method is applicable to shallow-focus earthquakes, and to earthquakes of large magnitude in which methods using S-wave polarization data and P-wave spectra are difficult to apply.

Waveform Characteristics and Focal Mechanism Solutions of Five Aftershocks of the 1983 Goodnow, New York, Earthquake by Polarization Analysis and Waveform Modeling

1991 ◽  
Vol 62 (2) ◽  
pp. 123-133 ◽  
Author(s):  
Zuyuan Liu ◽  
Robert. B. Herrmarnn ◽  
Jiakang Xie ◽  
E. Cranswick
Keyword(s):  
New York ◽  
Focal Mechanism ◽  
Fault Plane ◽  
Body Wave ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Systematic Search ◽  
P Wave ◽  
S Wave ◽  
Focal Mechanism Solutions

Abstract Waveforms of the direct P-, SV- and SH-waves of five 1983 Goodnow, New York, aftershocks (mb = 1.4–3.1), locally recorded at four hard-rock sites (epicentral distances=1.9–8.0 km) with GEOS systems, were studied to obtain their focal mechanism solutions by waveform fit using both systematic search and moment tensor inversion. Both synthetic and observed data were low-pass filtered at 10 Hz to reduce sensitivity to shallow earth structure. It was discovered that only the first cycle of P-wave and S-wave appear to have pure direct body wave characteristics. The strong P- and S-coda have no stable polarization. The five aftershocks have similar locations, identical P-first motions, but varying direct S-waveforms. A layered velocity model with a P-wave velocity of 4.4 km/s in the surface layer was derived. Fault plane solutions of four events indicate reverse faulting mechanisms that have a near horizontal P-axis with a strike of ENE. This is similar to the fault plane solution of the mainshock (October 7, 1983, mb = 5.1) and the composite focal mechanism of the aftershocks. Four aftershocks occurred on the fault planes with the strike NW-N and dip of 52°–64° toward NE-E. The fifth event studied has significant strike-slip motion with the P axis is also nearly horizontal and oriented NE. The results of systematic search technique agree well with those of moment tensor inversion. The first motion directions, pulse widths, amplitudes, amplitude ratios and arrival times of the direct P-, SV- and SH-phases of the synthetic seismograms are consistent with those of the observed seismograms. The results of the research demonstrated that the S-wave amplitude can provide important constraints on the focal mechanism.

scholarly journals Implications of 3D Seismic Raytracing on Focal Mechanism Determination

2019 ◽  
Vol 109 (6) ◽  
pp. 2746-2754
Author(s):  
Katharina Newrkla ◽  
Hasbi Ash Shiddiqi ◽  
Annie Elisabeth Jerkins ◽  
Henk Keers ◽  
Lars Ottemöller
Keyword(s):  
Focal Mechanism ◽  
Historical Earthquakes ◽  
Velocity Model ◽  
Waveform Data ◽  
Focal Mechanism Solutions ◽  
Velocity Models ◽  
Maximum Value ◽  
3D Velocity Model ◽  
First Motion

Abstract The purpose of this study is to investigate apparent first‐motion polarities mismatch at teleseismic distances in the determination of focal mechanism. We implement and compare four seismic raytracing algorithms to compute ray paths and travel times in 1D and 3D velocity models. We use the raytracing algorithms to calculate the takeoff angles from the hypocenter of the 24 August 2016 Mw 6.8 Chauk earthquake (depth 90 km) in central Myanmar to the stations BFO, GRFO, KONO, and ESK in Europe using a 3D velocity model of the upper mantle below Asia. The differences in the azimuthal angles calculated in the 1D and 3D velocity models are considerable and have a maximum value of 19.6°. Using the takeoff angles for the 3D velocity model, we are able to resolve an apparent polarity mismatch where these stations move from the dilatational to the compressional quadrant. The polarities of synthetic waveforms change accordingly when we take the takeoff angles corresponding to the 3D model into account. This method has the potential to improve the focal mechanism solutions, especially for historical earthquakes where limited waveform data are available.

A simple method for resolving large converted‐wave (P-SV) statics

Geophysics ◽  
1993 ◽  
Vol 58 (3) ◽  
pp. 429-433 ◽  
Author(s):  
Peter W. Cary ◽  
David W. S. Eaton
Keyword(s):  
P Wave ◽  
S Wave ◽  
Converted Wave ◽  
P Waves ◽  
Simple Method ◽  
Near Surface ◽  
S Waves ◽  
Static Solutions ◽  
Surface Fluctuations

The processing of converted‐wave (P-SV) seismic data requires certain special considerations, such as commonconversion‐point (CCP) binning techniques (Tessmer and Behle, 1988) and a modified normal moveout formula (Slotboom, 1990), that makes it different for processing conventional P-P data. However, from the processor’s perspective, the most problematic step is often the determination of residual S‐wave statics, which are commonly two to ten times greater than the P‐wave statics for the same location (Tatham and McCormack, 1991). Conventional residualstatics algorithms often produce numerous cycle skips when attempting to resolve very large statics. Unlike P‐waves, the velocity of S‐waves is virtually unaffected by near‐surface fluctuations in the water table (Figure 1). Hence, the P‐wave and S‐wave static solutions are largely unrelated to each other, so it is generally not feasible to approximate the S‐wave statics by simply scaling the known P‐wave static values (Anno, 1986).

The use of ScS-wave data in focal mechanism determinations

1962 ◽  
Vol 52 (3) ◽  
pp. 551-572
Author(s):  
Augustine S. Furumoto
Keyword(s):  
Focal Mechanism ◽  
Quantitative Relationship ◽  
P Wave ◽  
Wave Method ◽  
S Wave ◽  
Focal Mechanism Solutions ◽  
Wave Data

abstract In this paper the S wave method of focal mechanism determination is extended to include the ScS wave. By the establishment of the quantitative relationship between the directions of vibration of the S and the ScS, ScS wave data can be reduced to a form of S wave data usable for focal mechanism determinations. The new extension has been checked by reobtaining focal mechanism solutions for four heartquakes using ScS wave data. Results were consistent with previous solutions by the S wave method or P wave method.

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