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Regional Moment Tensor Solutions for Source-Type Identification: The Crandall Canyon Mine Collapse Douglas Dreger (Berkeley Seismological Laboratory), Sean Ford (Lawrence Livermore National Laboratory), William Walter (Lawrence Livermore National Laboratory) Seismic moment tensor methods are now routinely applied at many scales from the study of micro-earthquakes to the characterization of damaging great earthquakes, and applied at regional distances they are proving to be a reliable tool for distinguishing between earthquakes and events associated with volcanic processes [e.g. Dreger et al., 2000], and other man-made sources of seismic radiation such as from explosions, or mining activity [e.g. Ford et al., 2009]. On August 6, 2007 a magnitude 3.9 seismic event was associated with the tragic collapse of a Utah coal mine. The event was well recorded by UUSS, USGS, and Earthscope USAarray stations (Fig. 1) The moment tensor inversion of complete, three-component, low-frequency (0.02 to 0.10 Hz) displacement records recovers a mechanism that is most consistent with the gravity driven vertical collapse of a horizontally oriented underground cavity (Fig. 1a). The seismic moment tensor of the event, is comprised 78% from a closing horizontal crack and a secondary 22% non-crack component, which results from the fitting of the large amplitude Love waves that were observed on the tangential component (Fig. 1c). Plausible interpretations of the secondary source include sympathetic vertical dip-slip faulting, non-uniform crack closure, and elastic relaxation in response to the mine collapse [Ford et al., 2008]. The moment tensor solution produces a pure dilatational P-wave first-motion mechanism consistent with the P-wave polarity observations [Pechman et al., 2008]. The source-type diagram [Hudson et al., 1989] in Fig. 1a illustrates the deviation from a pure earthquake double-couple (DC) source at the center in terms of a volumetric component (explosion or implosion) on the ordinate, and deviatoric component in terms of a volume compensated linear vector dipole (CLVD) on the abscissa. The minecollapse event plots in the region of a negative or closing crack similar to solutions obtained for other mine and Nevada Test Site (NTS) cavity collapses [Ford et al., 2009]. The application of seismic moment tensor analysis to non-tectonic seismic events such as buried explosions or underground collapses as illustrated here, demonstrates the feasibility of continuous monitoring of regional distance seismic wavefields for source-type identification useful for nuclear explosion monitoring and possible emergency response. References Dreger, D. S., H. Tkalcic, and M. Johnston (2000). Dilational processes accompanying earthquakes in the Long Valley Caldera, Science, 288, 122-125. Ford, S., D. Dreger and W. Walter (2008). Source Characterization of the August 6, 2007 Crandall Canyon Mine Seismic Event in Central Utah, Seismol. Res. Lett., 79, 637-644. Ford, S. R., D. S. Dreger, and W. R. Walter (2009), Identifying isotropic events using a regional moment tensor inversion, J. Geophys. Res., 114, B01306. Acknowledgements: We acknowledge DOE BAA contract DE-FC52-06NA27324 (BSL) and Contract W-7405-Eng-48 (LLNL) for support of this work. Fig 1. A) Source type plot showing separation of earthquake, explosion and collapse (yellow star shows the 08/06/2007 mine-collapse event). B) Location of the 08/06/2007 mine-collapse event and the 6 closest stations. C) Observed (black) and predicted (red) displacement waveforms (0.02 to 0.1 Hz). II-92 | 2010 IRIS Core Programs Proposal | Volume II | Non-earthquake Seismic Sources
Source Analysis of the Memorial Day Explosion, Kimchaek, North Korea Sean R. Ford (Lawrence Livermore National Laboratory), William R. Walter (Lawrence Livermore National Laboratory), Douglas S. Dreger (Berkeley Seismological Laboratoy) We perform a series of source inversions for the 25 May 2009 (Memorial Day) North Korean seismic event using intermediate period (10-50s) complete waveform modeling using data housed at IRIS. An earthquake source is inconsistent with the data and the best-fit full seismic moment tensor is dominantly explosive (~60%) with a moment magnitude (Mw) of 4.5. A pure explosion solution yields a scalar seismic moment of 1.8e22 dyne-cm (Mw4.1) and fits the data almost as well as the full solution. The difference between the full and explosion solutions is the predicted fit to observed tangential displacement, which requires some type of non-isotropic (non-explosive) radiation. Possible causes of the tangential displacement are additional tectonic sources, tensile failure at depth, and anisotropic wave propagation. Similar displacements may be hidden in the noise of the 2006 event. Future analyses of this type could be used to identify and characterize non-earthquake events such as explosions and mine collapses. References Ford, S.R., D. Dreger, and W. R. Walter, Source analysis of the Memorial Day explosion, Kimchaek, North Korea, Geophys. Res. Lett., 36 (L21304), 2009 Acknowledgements: We acknowledge DOE BAA contract DE-FC52-06NA27324 (BSL) and Contract W-7405-Eng-48 (LLNL) for suppor a) Models and waveforms P T Best-full (4.5) Best-dev (4.3) Best-dc (4.4) Best-iso (4.1) MDJ 6 o 371 km 1560 nm INCN 207 o 473 km 1180 nm TJN 196 o 566 km 1030 nm BJT 267 o 1099 km 864 nm HIA 324 o 1147 km 106 nm T R V b) Source-type plot Explosion 75 Best-iso 32 s 48 s +Dipole +Crack 81 Best-full +CLVD Best-dc 52 DC 80 Best-dev –CLVD Implosion Events from NTS study by Ford et al. [2009] Earthquake Explosion a) Models and their respective forward-predicted waveforms as a function of color compared with the actual waveforms (black line) all filtered between 10-50 sec period. b) Source-type plot with various solutions corresponding to the models given in a) and their associated fit percent. 2010 IRIS Core Programs Proposal | Volume II | Non-earthquake Seismic Sources | II-93
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volume ii - accomplishments Facilit
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volume ii - accomplishments Facilit
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CONTENTS Introduction..............
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Non-Volcanic Tremor along the Oaxac
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Detecting the Limit of Slab Break-o
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Lower Mantle, Core-Mantle Boundary
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• Non-Earthquake Seismic Sources
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acoustics community by permitting a
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Near-Surface Environments - Hazards
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Why Do Faults Slip? Emily Brodsky (
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Another probe of fault evolution is
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to provide a best match with the Gl
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tectonic disruption and mass accumu
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W3 ∆ 5 . A number of intriguing r
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thermal and compositional effects r
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Towards a Global School Seismic Net
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On-Line Seismology Curriculum for U
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Teachers on the Leading Edge: Earth
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USArray Education and Outreach in S
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From an IRIS Lecture Tour to a Gene
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Explorer Series Robert Bartolotta (
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Workshop “Earth System Science fo
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The IRIS Internship Cycle: From Int
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Community-Outreach Efforts in Data
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Site Reconnaissance for Earthscope
Page 53 and 54: jAmaseis: Seismology Software Meeti
Page 55 and 56: Near Real-Time Simulations of Globa
Page 57 and 58: FuncLab: A MATLAB Interactive Toolb
Page 59 and 60: Five Years of Distributing the Seis
Page 61 and 62: IRIS DMS Data Products, Beyond Raw
Page 63 and 64: Local Earthquakes in the Dallas-Ft.
Page 65 and 66: Epicentral Location Based on Raylei
Page 67 and 68: Analysis of Spatial and Temporal Se
Page 69 and 70: Exceptional Ground Motions from the
Page 71 and 72: The 2010 Mw7.2 El Mayor-Cucapah Ear
Page 73 and 74: Effects of Kinematic Constraints on
Page 75 and 76: Imaging of the Source Properties of
Page 77 and 78: Teleseismic Inversion for Rupture P
Page 79 and 80: The Global Aftershocks of the 2004
Page 81 and 82: The 17 July 2006 Java Tsunami Earth
Page 83 and 84: Seismic Cycles on Oceanic Transform
Page 85 and 86: Migration of Early Aftershocks Foll
Page 87 and 88: Apparent Stress Variations at the O
Page 89 and 90: Automated Identification of Telesei
Page 91 and 92: Evaluating Ground Motion Prediction
Page 93 and 94: Tremor Monitoring Aaron Wech (Unive
Page 95 and 96: Slow Slip and Tremor in the Norther
Page 97 and 98: 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2
Page 99 and 100: Intimate Details of Tremor Observed
Page 101 and 102: Global Search of Triggered Tremor a
Page 103: Slab Morphology in the Cascadia For
Page 107 and 108: Iceberg Tremor and Ocean Signals Ob
Page 109 and 110: Elucidating the Stick-Slip Nature o
Page 111 and 112: Probing the Atmosphere and Atmosphe
Page 113 and 114: Volcanic Plume Height Measured by S
Page 115 and 116: Eruption Dynamics at Mount St. Hele
Page 117 and 118: A Search for the Lunar Core Using A
Page 119 and 120: Seismic Imaging of the Mt. Rose Fau
Page 121 and 122: Structure of the California Coast R
Page 123 and 124: Temporal Variations in Crustal Scat
Page 125 and 126: High-Resolution Locations of Trigge
Page 127 and 128: Adjoint Tomography of the Southern
Page 129 and 130: Crustal Structure of the High Lava
Page 131 and 132: Controlled Source Seismic Experimen
Page 133 and 134: Structural Interpretations Based on
Page 135 and 136: Optimized Velocities and Prestack D
Page 137 and 138: 40 Crustal Structure beneath the Hi
Page 139 and 140: Controlled-Source Seismic Investiga
Page 141 and 142: Northward Thinning of Tibetan Crust
Page 143 and 144: An Integrated Analysis of an Ancien
Page 145 and 146: Crustal Velocity Structure of Turke
Page 147 and 148: Ambient Noise Tomography of the Pam
Page 149 and 150: Ambient Noise Monitoring of Seismic
Page 151 and 152: Mushy Magma beneath Yellowstone Ris
Page 153 and 154: Imaging the Seattle Basin to Improv
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Developing a Database of ENA Ground
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Lithospheric Layering in the North
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eflective zones on depthmigrated se
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FischerFig05.pdf 1 2/8/10 12:31 PM
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S-Velocity Structure of Cratons, fr
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Seismic Structure of the Crust and
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Subducted Oceanic Asthenosphere and
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Detecting the Limit of Slab Break-o
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Pn Tomography of the Western United
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3-D Isotropic Shear Velocity Model
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Seismic Anisotropy Associated with
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Anisotropy in the Great Basin from
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Source-Side Shear Wave Splitting an
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S-Velocity Structure of the Upper M
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Velocity Structure of the Western U
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Segmented African Lithosphere benea
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Imaging the Mantle Wedge in the Cen
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A Slab Remnant beneath the Gulf of
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Imaging the Southern Alaska Subduct
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Opposing Slabs under Northern South
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Effect of Prior Petrological Constr
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Global Azimuthal Seismic Anisotropy
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The Stratification of Seismic Azimu
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Upper Mantle Anisotropy beneath the
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The Teleseismic Signature of Fossil
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Seismic Anisotropy under Central Al
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Stress-Induced Upper Crustal Anisot
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Tau-p Depropagation of Five Regiona
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Mapping the Upper Mantle with the S
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Upper Mantle Structure of Southern
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The Africa-Europe Plate Boundary in
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The Isabella Anomaly Imaged by Eart
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Tomographic Image of the Crust and
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Small-Scale Mantle Heterogeneity an
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Mantle Heterogeneity West and East
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New Geophysical Insight into the Or
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The Plume-slab Interaction beneath
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Imaging the Shear Wave Velocity "Pl
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Slab Fragmentation and Edge Flow: I
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Mantle Shear-Wave Velocity Structur
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Discordant Contrasts of P- and S-Wa
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Upper Mantle Discontinuity Topograp
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Edge-Driven Convection beneath the
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Imaging Attenuation in the Upper Ma
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Three-Dimensional Electrical Conduc
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Core-Mantle Boundary Heat Flow Thor
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Constraints on Lowermost Mantle Ani
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Localized Double-Array Stacking Ana
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Waveform Modeling of D" Discontinui
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Absence of Ultra-Low Velocity Zones
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Moving Seismic Tomography Beyond Fa
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A Three-Dimensional Radially Anisot
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The Importance of Crustal Correctio
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Slabs Do Not Go Gentle Karin Sigloc
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Localized Temporal Change of the Ea
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Core Structure Reexamined Using New
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Large Variations in Travel Times of
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Observations of Antipodal PKIIKP Wa
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Regional Variation of Inner Core An
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Wide-Scale Detection of Earthquake
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