Source type plot for inversion of the moment tensor

Hudson, John; Pearce, Robert G.; Rogers, Richard M.

doi:10.1029/jb094ib01p00765

Cited by 340 publications

(220 citation statements)

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“…Following Hudson et al (1989) we visualize the nature of the calculated moment tensors using source-type plots. These equal-area plots are a means to illustrate how strong the isotropic component is (k parameter, near-horizontal lines) and how much the deviatoric component differs from a pure double couple (T parameter, near-vertical lines).…”

Section: Source Discriminationmentioning

confidence: 99%

“…These equal-area plots are a means to illustrate how strong the isotropic component is (k parameter, near-horizontal lines) and how much the deviatoric component differs from a pure double couple (T parameter, near-vertical lines). Ⓔ More information on source-type plots is given in Background Information on Moment Tensor Inversions and Grid for Source-Type Plots after Hudson et al (1989) in the electronic edition of BSSA.…”

Section: Source Discriminationmentioning

confidence: 99%

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Moment Tensor Inversions of Icequakes on Gornergletscher, Switzerland

Walter

Clinton²,

Deichmann³

et al. 2009

Bulletin of the Seismological Society of America

109

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We have determined seismic source mechanisms for shallow and intermediate-depth icequake clusters recorded on the glacier Gornergletscher, Switzerland, during the summers of 2004 and 2006. The selected seismic events are part of a large data set of over 80,000 seismic events acquired with a dense seismic network deployed in order to study the yearly rapid drainage of Gornersee lake, a nearby icemarginal lake. Using simple frequency and distance scaling and Green's functions for a homogeneous half-space, we calculated moment tensor solutions for icequakes with M w 1:5 using a full-waveform inversion method usually applied to moderate seismic events (M w > 4) recorded at local to regional distances (≈50-700 km). Inversions from typical shallow events are shown to represent tensile crack openings. This explains well the dominating Rayleigh waves and compressive first motions observed at all recording seismograms. As these characteristics can be observed in most icequake signals, we believe that the vast majority of icequakes recorded in the 2 yr is due to tensile faulting, most likely caused by surface crevasse openings. We also identified a shallow cluster with somewhat atypical waveforms in that they show less dominant Rayleigh waves and quadrantal radiation patterns of first motions. Their moment tensors are dominated by a large double-couple component, which is strong evidence for shear faulting. Although less than a dozen such icequakes have been identified, this is a substantial result as it shows that shear faulting in glacier ice is generally possible even in the absence of extreme flow changes such as during glacier surges. A third source of icequakes was located at 100 m depth. These sources can be represented by tensile crack openings. Because of the high-hydrostatic pressure within the ice at these depths, these events are most likely related to the presence of water lenses that reduce the effective stress to allow for tensile faulting.Online Material: Background information and results of moment tensor inversions.

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Section: Source Discriminationmentioning

confidence: 99%

Section: Source Discriminationmentioning

confidence: 99%

Moment Tensor Inversions of Icequakes on Gornergletscher, Switzerland

Walter

Clinton²,

Deichmann³

et al. 2009

Bulletin of the Seismological Society of America

109

View full text Add to dashboard Cite

show abstract

“…The source-type parameters (Hudson et al, 1989) are calculated for each synthetic source ( Figure S1b). Since the source-type plot does not account for total seismic moment (only relative moment) or source orientation, a single set of source-type parameters (one point on the sourcetype plot) can represent several sources.…”

Section: Bssa Short Notementioning

confidence: 99%

“…Mechanism distribution is plotted with a Riedesel and Jordan (1989) plot, which is also the preference of many of the previously mentioned studies. In the following study we will employ the source-type plot from Hudson et al (1989), which is described in Ford et al (2009). Further details of the inversion method and its practical implementation are also given in Ford et al (2009).…”

Section: Introductionmentioning

confidence: 99%

Network Sensitivity Solutions for Regional Moment-Tensor Inversions

Ford¹,

Dreger²,

Walter³

2010

Bulletin of the Seismological Society of America

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“…This decomposition was further developed and applied by Sipkin (1986), Jost and Herrmann (1989), Hudson et al (1989), Kuge and Lay (1994), Vavryčuk (2001Vavryčuk ( , 2005Vavryčuk ( , 2011 and others. Furthermore, Hudson et al (1989) and Riedesel and Jordan (1989) proposed graphical representations of the DC and non-DC components in order to identify visually the most appropriate physical source corresponding to the retrieved moment tensor (for a geometric comparison of both approaches, see Tape and Tape 2012b).Since an increasing quantity and quality of seismic data allow inverting for accurate moment tensors and interpreting the details of the source process, an efficient and physically reasonable decomposition of moment tensors is necessary. This has recently motivated several authors to revisit the existing decompositions (Chapman and Leaney 2012; Zhu and Ben-Zion 2013) and sourcetype plots (Chapman and Leaney 2012; Tape and Tape 2012a, b) and to develop their modifications.…”

mentioning

confidence: 99%

Moment tensor decompositions revisited

2014

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The decomposition of moment tensors into isotropic (ISO), double-couple (DC) and compensated linear vector dipole (CLVD) components is a tool for classifying and physically interpreting seismic sources. Since an increasing quantity and quality of seismic data allow inverting for accurate moment tensors and interpreting details of the source process, an efficient and physically reasonable decomposition of moment and source tensors is necessary. In this paper, the most common moment tensor decompositions are revisited, new equivalent formulas of the decompositions are derived, suitable norms of the moment tensors are discussed and the properties of commonly used source-type plots are analysed. The Hudson skewed diamond plot is introduced in a much simpler way than originally proposed. It is shown that not only the Hudson plot but also the diamond CLVD-ISO plot and the Riedesel-Jordan plot conserve the uniform distribution probability of moment eigenvalues if the appropriate norm of moment tensors is applied. When analysing moment tensor uncertainties, no source-type plot is clearly preferable. Since the errors in the eigenvectors and eigenvalues of the moment tensors cannot be easily separated, the moment tensor uncertainties project into the source-type plots in a complicated way. As a consequence, the moment tensors with the same uncertainties project into clusters of a different size. In case of an anisotropic focal area, the complexity of moment tensors of earthquakes prevents their direct interpretation, and the decomposition of moment tensors must be substituted by that of the source tensors.Keywords Dynamics and mechanics of faulting . Earthquake source observations . Seismic anisotropy . Theoretical seismology IntroductionThe moment tensor describes equivalent body forces acting at a seismic point source (Burridge and Knopoff 1964) and is a basic quantity evaluated for earthquakes on all scales from acoustic emissions to large devastating earthquakes. The most common type of the moment tensor is the double-couple (DC) source which represents the force equivalent of shear faulting on a planar fault in isotropic media. However, many studies reveal that seismic sources often display more general moment tensors with significant non-double-couple (non-DC) components ). An explosion is an obvious example of a non-DC source, but non-DC components can also be produced by the collapse of a cavity in mines (Rudajev and Šílený 1985;Šílený and Milev 2008), by shear faulting on a nonplanar (curved or irregular) fault (Sipkin 1986), by tensile faulting induced by fluid injection in geothermal or volcanic areas (Ross et al. 1996;Julian et al. 1997) when the slip vector is inclined from the fault and causes its opening (Vavryčuk 2001(Vavryčuk , 2011 Roessler et al. 2004Roessler et al. , 2007. Complications also arise if the source is situated at a material interface (Vavryčuk 2013).In order to identify which type of seismic source is physically represented by the retrieved moment tensor, Knopoff and Randall (1970...

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Source type plot for inversion of the moment tensor

Cited by 340 publications

References 9 publications

Moment Tensor Inversions of Icequakes on Gornergletscher, Switzerland

Moment Tensor Inversions of Icequakes on Gornergletscher, Switzerland

Network Sensitivity Solutions for Regional Moment-Tensor Inversions

Moment tensor decompositions revisited

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