Automatic determination of focal mechanism solutions using initial motion polarities of P and S waves

2004 ◽  
Vol 146 (3-4) ◽  
pp. 531-549 ◽  
Author(s):  
Masaki Nakamura
Keyword(s):  
Focal Mechanism ◽  
Automatic Determination ◽  
S Waves ◽  
Focal Mechanism Solutions ◽  
Initial Motion

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.

scholarly journals FOCAL MECHANISM OF THE LITHUANIAN EARTHQUAKE OF BASED ON WAVEFORM INVERSION

2021 ◽  
pp. 46-52
Author(s):  
D. Malytskyy ◽  
V. Ņikuļins
Keyword(s):  
Focal Mechanism ◽  
Moment Tensor ◽  
Waveform Inversion ◽  
Forward Modeling ◽  
Seismic Wave Propagation ◽  
Practical Significance ◽  
Numerical Techniques ◽  
Baltic Region ◽  
S Waves

The aim: Determination of focal mechanism of Lithuanian earthquake of 12.06.15 (t0 = 08:18:26.4; 55.52° N, 21.40° E; hs = 0.9 км.; ML = 2.6) by waveform inversion using direct waves and a limited number of stations. Method: Matrix method is used for modelling of seismic wave propagation in the medium modelled as horizontally layered heterogeneous elastic structure. There were obtained the relations of displacement waves on the free surface that were used for seismic tensor determination using only direct P- and S- waves. Determination of seismic tensor and the focal mechanism on the base of developed method for a point source is described. Thus, based on forward modeling, numerical techniques are developed for the inversion of observed waveforms for the components of moment tensor. Results: In the paper, a method is presented for the focal mechanism determination of Lithuanian earthquake of 12.06.15 (ML = 2.6) by waveform inversion using limited number of stations. The focal mechanism is determined using the data from two stations: PABE, SLIТ and from three stations: PABE, MTSE, SLIТ. These seismic stations are the part of BAVSEN (BalticVirtualSeismicNetwork). Scientific novelty: 1. In the paper, a method is presented for moment tensor inversion for the focal mechanism determination of events with a low seismicity. The East Baltic region (EBR) is the region with low seismicity. 2. The focal mechanism is determined using the data from a limited number of stations. Practical significance: The results of focal mechanism determination can be used to study seismicity for regions with a low seismicity using a limited number of stations.

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.

Focal mechanisms of Indian earthquakes

1972 ◽  
Vol 62 (2) ◽  
pp. 603-608 ◽  
Author(s):  
A. R. Banghar
Keyword(s):  
Focal Mechanism ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Peninsular India ◽  
S Waves ◽  
Focal Mechanism Solutions

abstract Focal mechanism solutions are presented for two earthquakes that occurred in peninsular India. The first motions of P, PKP and the polarization (or first motions) of S waves were used for this investigation. Both of these mechanisms are found to be associated with strike-slip faulting.

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.

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