The ISC Bulletin as a comprehensive source of earthquake source mechanisms

Abstract. In this article we summarize the availability of earthquake source mechanisms in the Bulletin of the International Seismological Centre (ISC). The bulletin in its current status contains ∼81 000 seismic events with only one associated mechanism solution and ∼25 000 events with at least two associated source mechanisms. The main sources of earthquake mechanisms in the ISC Bulletin are reported solutions provided by data contributors and ISC-computed focal mechanisms based on first motion polarities. Given the importance of using pre-determined fault plane solutions in different types of studies, here we briefly discuss the methodologies adopted by major data providers to the ISC and investigate the intra-event variability of the source mechanisms. We conclude that the overall agreement among different earthquake mechanisms for the same event as reported by different sources can show a similarity coefficient as high as 80 %, based on the rotation angles of their best-fitting double couple solutions, for the majority of the cases. The earthquake source mechanisms discussed in this work are freely available within the ISC Bulletin websearch at http://doi.org/10.31905/D808B830 .

[1]  John D. Hunter,et al.  Matplotlib: A 2D Graphics Environment , 2007, Computing in Science & Engineering.

[2]  Torsten Dahm,et al.  Seismicity monitoring by cluster analysis of moment tensors , 2014 .

[3]  E. Okal.  “Detached” deep earthquakes: are they really? , 2001 .

[4]  D. Storchak,et al.  A scheme to set preferred magnitudes in the ISC Bulletin , 2016, Journal of Seismology.

[5]  Hiroo Kanamori,et al.  W phase source inversion for moderate to large earthquakes (1990–2010) , 2012 .

[6]  Peter M. Shearer,et al.  Evidence from a cluster of small earthquakes for a fault at 18 km depth beneath Oak Ridge, southern California , 1998, Bulletin of the Seismological Society of America.

[7]  H. Kanamori,et al.  Assessment of teleseismically-determined source parameters for the April 25, 2015 MW 7.9 Gorkha, Nepal earthquake and the May 12, 2015 MW 7.2 aftershock , 2017 .

[8]  R. Herrmann,et al.  Rapid Estimates of the Source Time Function and Mw using Empirical Green’s Function Deconvolution , 2014 .

[9]  E. R. Engdahl,et al.  Constraints on seismic velocities in the Earth from traveltimes , 1995 .

[10]  K. Lentas.  Towards routine determination of focal mechanisms obtained from first motion P-wave arrivals , 2018 .

[11]  B. Célérier.  Remarks on the relationship between the tectonic regime, the rake of the slip vectors, the dip of the nodal planes, and the plunges of the P, B, and T axes of earthquake focal mechanisms , 2010 .

[12]  R. Bürgmann,et al.  The 2013 Okhotsk deep‐focus earthquake: Rupture beyond the metastable olivine wedge and thermally controlled rise time near the edge of a slab , 2014 .

[13]  S. Beck,et al.  Source process of the 3 November 2002 Denali fault earthquake (central Alaska) from teleseismic observations , 2003 .

[14]  H. Kanamori,et al.  The December 7, 2012 Japan Trench intraplate doublet (Mw 7.2, 7.1) and interactions between near-trench intraplate thrust and normal faulting , 2013 .

[15]  Hiroo Kanamori,et al.  Source inversion of W phase: speeding up seismic tsunami warning , 2008 .

[16]  Hiroo Kanamori,et al.  Rupture characteristics of major and great (Mw  ≥ 7.0) megathrust earthquakes from 1990 to 2015: 1. Source parameter scaling relationships , 2016 .

[17]  Anthony Lomax,et al.  Mwpd: A duration–amplitude procedure for rapid determination of earthquake magnitude and tsunamigenic potential from P waveforms , 2009 .

[18]  Y. Y.,et al.  3-D rotation of double-couple earthquake sources , 2006 .

[19]  Barbara Romanowicz,et al.  Global scale observations of scattered energy near the inner-core boundary: Seismic constraints on the base of the outer-core , 2015 .

[20]  Göran Ekström,et al.  The global CMT project 2004–2010: Centroid-moment tensors for 13,017 earthquakes , 2012 .

[21]  E. Okal,et al.  Centroid moment tensor solutions for deep earthquakes predating the digital era: the World-Wide Standardized Seismograph Network dataset (1962–1976) , 1997 .

[22]  M. Zoback.  First‐ and second‐order patterns of stress in the lithosphere: The World Stress Map Project , 1992 .

[23]  Paul G. Richards,et al.  Quantitative Seismology: Theory and Methods , 1980 .

[24]  D. Storchak,et al.  Rebuild of the Bulletin of the International Seismological Centre (ISC), part 1: 1964–1979 , 2017, Geoscience Letters.

[25]  A. Dziewoński,et al.  Multiple CMT source analysis of the 2004 Sumatra earthquake , 2005 .

[26]  David J. Wald,et al.  Slab1.0: A three‐dimensional model of global subduction zone geometries , 2012 .

[27]  E. Engdahl,et al.  ISC-EHB: reconstruction of a robust earthquake data set , 2018 .

[28]  John H. Woodhouse,et al.  Determination of earthquake source parameters from waveform data for studies of global and regional seismicity , 1981 .

[29]  H. Kanamori,et al.  Recurring large deep earthquakes in Hindu Kush driven by a sinking slab , 2016 .

[30]  Manfred Baer,et al.  Regional moment tensor determination in the European–Mediterranean area — initial results , 2002 .

[31]  E. Okal,et al.  Tsunami earthquakes: the quest for a regional signal , 2001 .

[32]  M. Vallée,et al.  SCARDEC: a new technique for the rapid determination of seismic moment magnitude, focal mechanism and source time functions for large earthquakes using body‐wave deconvolution , 2011 .

[33]  C. Frohlich.  Triangle diagrams: ternary graphs to display similarity and diversity of earthquake focal mechanisms , 1992 .

[34]  D. Storchak,et al.  Improved location procedures at the International Seismological Centre , 2011 .

[35]  E. Okal,et al.  Centroid moment tensor solutions for intermediate-depth earthquakes of the WWSSN-HGLP era (1962-1975) , 2001 .

[36]  H. Kanamori,et al.  Source Inversion of the W-Phase: Real-time Implementation and Extension to Low Magnitudes , 2009 .

[37]  G. Helffrich.  How good are routinely determined focal mechanisms? Empirical statistics based on a comparison of Harvard, USGS and ERI moment tensors , 1997 .

[38]  Mizuho Ishida,et al.  Automated Seismic Moment Tensor Determination by Using On-line Broadband Seismic Waveforms , 1998 .

[39]  Akira Hasegawa,et al.  Change in stress field after the 2011 great Tohoku-Oki earthquake , 2012 .

[40]  Mehdi Rezapour,et al.  Bias in surface-wave magnitude Ms due to inadequate distance corrections , 1998, Bulletin of the Seismological Society of America.

[41]  Remko Scharroo,et al.  Generic Mapping Tools: Improved Version Released , 2013 .

[42]  E. Boschi,et al.  European–Mediterranean Regional Centroid Moment Tensor catalog: Solutions for 2005–2008 , 2011 .

[43]  Ruifeng Liu,et al.  First Application of the New IASPEI Teleseismic Magnitude Standards to Data of the China National Seismographic Network , 2009 .

[44]  David Oppenheimer,et al.  FPFIT, FPPLOT and FPPAGE; Fortran computer programs for calculating and displaying earthquake fault-plane solutions , 1985 .

[45]  M. Wysession,et al.  Geographic variations in lowermost mantle structure from the ray parameters and decay constants of core‐diffracted waves , 2017 .

[46]  C. Frohlich,et al.  How well constrained are well‐constrained T, B, and P axes in moment tensor catalogs? , 1999 .

[47]  S. Dosso,et al.  Mapping crustal stress and strain in southwest British Columbia , 2011 .

[48]  Dmitry A. Storchak,et al.  Data Collection at the International Seismological Centre , 2001 .

[49]  E. Clévédé,et al.  Source models of great earthquakes from ultra low-frequency normal mode data , 2014 .