scholarly journals Generalized orthonormal moment tensor decomposition and its source-type diagram

2020 ◽  
Author(s):  
Ting-Chung Huang ◽  
Yih-Min Wu
Keyword(s):  
Seismic Moment ◽  
Decomposition Method ◽  
Moment Tensor ◽  
Tensor Decomposition ◽  
New Method ◽  
Seismic Moment Tensor ◽  
Linear Vector ◽  
Source Type ◽  
Sign Problem ◽  
Double Couple

Abstract Moment tensor decomposition is a method for deriving the isotropic (ISO), double-couple (DC), and compensated linear vector dipole (CLVD) components from a seismic moment tensor. Currently, there are two families of methods, namely, standard moment tensor decomposition and Euclidean moment tensor decomposition. Although both methods can usually provide workable solutions, there are some minor inconsistencies between the two methods: an equality inconsistency that occurs in standard moment tensor decomposition and the pure CLVD unity and flip basis inconsistency encountered in Euclidean moment tensor decomposition. Moreover, there is a sign problem when disentangling the CLVD component from a DC-dominated case. To address these minor inconsistencies, we propose a new moment tensor decomposition method inspired by both previous methods. The new method can not only avoid all these minor inconsistencies but also withstand deviations in ISO- or CLVD-dominated cases when using source-type diagrams.

Analysis of non-double-couple source mechanisms in an area of induced seismicity, West Texas (USA).

2021 ◽  
Author(s):  
Savvaidis Alexandros ◽  
Roselli Pamela
Keyword(s):  
Stress Field ◽  
Time Domain ◽  
Seismic Moment ◽  
Moment Tensor ◽  
P Wave ◽  
Seismic Moment Tensor ◽  
Ground Displacement ◽  
Moment Tensors ◽  
West Texas ◽  
Double Couple

<p>In the scope to investigate the possible interactions between injected fluids, subsurface geology, stress field and triggering earthquakes, we investigate seismic source parameters related to the seismicity in West Texas (USA). The analysis of seismic moment tensor is an excellent tool to understand earthquake source process kinematics; moreover, changes in the fluid volume during faulting leads to existence of non-double-couple (NDC) components (Frohlich, 1994; Julian et al., 1998; Miller et al., 1998). The NDC percentage in the source constitutes the sum of absolute ISO and CLVD components so that %NDC= % ISO + %CLVD and %ISO+%CLVD+%DC=100%. It is currently known that the presence of NDC implies more complex sources (mixed shear-tensile earthquakes) correlated to fluid injections, geothermal systems and volcano-seismology where induced and triggered seismicity is observed.</p><p>With this hypothesis, we analyze the micro-earthquakes (M <2 .7) recorded by the Texas Seismological Network (TexNet) and a temporary network constituted by 40 seismic stations (equipped by either broadband or 3 component geophones). Our study area is characterized by Northwest-Southeast faults that follow the local stress/field (SH<sub>max</sub>) and the geological characteristic of the shallow basin structure of the study area. After a selection based on signal-to-noise ratio, we filter (1-50 Hz) the seismograms and estimate P-wave pulse polarities and the first P-wave ground displacement pulse in time domain. Then, we perform the full moment tensor analysis by using hybridMT technique (Andersen, 2001; Kwiatek et al., 2016) with a detailed 1D velocity model. The key parameter is the polarity/area of the first P-wave ground displacement pulse in time domain. Uncertainties of estimated moment tensors are expressed by normalized root-mean-square (RMS errors) between theoretical and estimated amplitudes (Vavricuk et al., 2014). We also evaluate the quality of the seismic moment tensors by bootstrap and resampling. In our preliminary results we obtain NDC percentage (in terms of %ISO and %CLVD components), Mw, seismic moment, P, T and B axes orientation for each source inverted.</p>

scholarly journals Non double couple seismic sources, faults interaction and hypothesis of self-organized criticality

2005 ◽  
Vol 5 (1) ◽  
pp. 11-15 ◽  
Author(s):  
S. Yunga ◽  
A. Lutikov ◽  
O. Molchanov
Keyword(s):  
Seismic Moment ◽  
Moment Tensor ◽  
Regional Scale ◽  
Small Scale ◽  
Scaling Relations ◽  
Seismic Moment Tensor ◽  
Data Set ◽  
Geological Unit ◽  
Double Couple ◽  
Deformation Modes

Abstract. Non double couple (NDC) sources are considered in framework of the hypothesis that the process of seismic rupture can be viewed as a result of complicated fault geometry and its segmentation. Analytical approach is found to reveal reliability of NDC measure taking into consideration the values of seismic moment tensor errors. The study focuses on the comparison of the deformation modes of the NDC sources with the stress states in its vicinity. The deformation modes of faulting and fracturing at a small scale in NDC earthquake focus and at regional scale in geological unit were investigated using at the last case summation of seismic moment tensors. These local and regional deformation modes in some of geodynamic regimes confirm the self-similarity assumption. For the whole data set scaling relations seem to be more complicated. This feature implies that besides stresses second order factors, as the hydrothermal or magmatic pore fluids in rock, influence source characteristics and bring new complications in scaling relations.

Defining the scalar moment of a seismic source with a general moment tensor

1999 ◽  
Vol 89 (5) ◽  
pp. 1390-1394 ◽  
Author(s):  
David Bowers ◽  
John A. Hudson
Keyword(s):  
Seismic Moment ◽  
Moment Tensor ◽  
Seismic Source ◽  
Second Order ◽  
Seismic Moment Tensor ◽  
Total Moment ◽  
Double Couple ◽  
The Moment ◽  
Deviatoric Part ◽  
Scalar Moment

Abstract We compare several published definitions of the scalar moment M0, a measure of the size of a seismic disturbance derived from the second-order seismic moment tensor M (with eigenvalues m1 ≥ m3 ≥ m2). While arbitrary, a useful definition is in terms of a total moment, MT0 = MI + MD, where MI = |M|, with M = (m1 + m2 + m3)/3, is the isotropic moment, and MD = max(|mj − M|; j = 1, 2, 3), is the deviatoric moment. This definition is consistent with other definitions of M0 if M is a double couple. This definition also gives physically appealing and simple results for the explosion and crack sources. Furthermore, our definitions of MT0, MI and MD are in accord with the parameterization of the moment tensor into a deviatoric part (represented by T which lies in [−1,1]) and a volumetric part (represented by k which lies in [−1, 1]) proposed by Hudson et al. (1989).

A technique for the recovery of the seismic moment tensor applied to the Oaxaca, Mexico earthquake of November 1978

1980 ◽  
Vol 70 (3) ◽  
pp. 717-734
Author(s):  
Steven N. Ward
Keyword(s):  
Seismic Moment ◽  
Statistical Tests ◽  
Weighted Least Squares ◽  
Moment Tensor ◽  
Source Parameters ◽  
Seismic Moment Tensor ◽  
Linear Inversion ◽  
Slip Vector ◽  
Double Couple ◽  
Mexico Earthquake

abstract The potential for using seismograms in a linear inversion process to recover the seismic moment tensor has been theorized for sometime. Unfortunately, practical application of the theory is difficult. Lateral variations of the Earth and imprecise knowledge of the source often severely contaminate real seismic data relative to synthetic models which must be supplied. This paper outlines an experiment which minimizes the contamination sufficiently to permit a successful inversion yet retains much of the data's sensitivity to source parameters. Routineness of technique was maintained in data selection and preparation by an unambiguous on-line windowing of P phases from the SRO network. Duplicate preparation of the theoretical P phases assured their synchronization with the observations. A time domain weighted least-squares inversion was implemented including double couple and nondouble couple constraints. Estimates of the total variance in addition to variances of the moment tensor eigenvalues and eigenvectors were returned, forming the basis for statistical tests. Seismic moments of 1.4 ± 0.4, 2.8 ± 0.3, and 2.7 ± 0.2 ×1027 dyne-cm were found for the Oaxaca, Mexico earthquake of November 1978, using 10 P phases in the distance ranges 20 to 120°, 25 to 120°, and 40 to 120°, respectively. Corresponding azimuth and dips of the probable slip vector are 21.5°, 11.8°; 30.3°, 9.3°; and 32.1°, 9.0°. No evidence was found to support the hypothesis that unconstrained source models fit the data significantly better than a double couple. We believe an automated procedure such as this is a viable means for the routine recovery and cataloging of earthquake sources.

scholarly journals Parametrization of general seismic potency and moment tensors for source inversion of seismic waveform data

2013 ◽  
Vol 194 (2) ◽  
pp. 839-843 ◽  
Author(s):  
Lupei Zhu ◽  
Yehuda Ben-Zion
Keyword(s):  
Moment Tensor ◽  
Relative Size ◽  
Seismic Moment Tensor ◽  
Source Inversion ◽  
Waveform Data ◽  
Moment Tensors ◽  
Linear Vector ◽  
Seismic Waveform ◽  
Isotropic Media ◽  
Double Couple

Abstract We decompose a general seismic potency tensor into isotropic tensor, double-couple tensor and compensated linear vector dipole using the eigenvectors and eigenvalues of the full tensor. Two dimensionless parameters are used to quantify the size of the isotropic and compensated linear vector dipole components. The parameters have well-defined finite ranges and are suited for non-linear inversions of source tensors from seismic waveform data. The decomposition and parametrization for the potency tensor are used to obtain corresponding results for a general seismic moment tensor. The relations between different parameters of the potency and moment tensors in isotropic media are derived. We also discuss appropriate specification of the relative size of different source components in inversions of seismic data.

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