Patricia A. McCrory, James Luke Blair September, 2006 Unknown First vector digital data USGS Information Services, Box 25286, Denver Federal Center, Denver, CO, 80225 United States Geological Survey http://pubs.usgs.gov/ds/91/ United States Geological Survey, Earthquake Hazards Team, September, 2006 Unknown First http://geopubs.wr.usgs.gov/*****/ hypos_below_slab_GCS_wgs84 DEPTH TO THE JUAN DE FUCA SLAB BENEATH THE CASCADIA SUBDUCTION MARGIN: A 3D MODEL FOR SORTING EARTHQUAKES By P. A. McCrory, J. L. Blair, D. H. Oppenheimer, and S. R. Walter 2006, Version 1.2 OVERVIEW OF THE SLAB-GRID PROJECT We present an updated model of the Juan de Fuca slab beneath southern British Columbia, Washington, Oregon, and northern California, and use this model to separate earthquakes occurring above and below the slab surface. The model is based on depth contours previously published by Flück and others (1997). Our model attempts to rectify a number of shortcomings in the original model and update it with new work. The most significant improvements include 1) a gridded slab surface in geo-referenced (ArcGIS) format, 2) continuation of the slab surface to its full northern and southern edges, 3) extension of the slab surface from 50-km depth down to 110-km, beneath the Cascade arc volcanoes, and 4) revision of the slab shape based on new seismic reflection and seismic refraction studies. We have used this surface to sort earthquakes, and present some general observations and interpretations of seismicity patterns revealed by our analysis. In addition, we provide files of earthquakes above and below the slab surface, and a 3D animation or fly-through showing a shaded relief map with plate boundaries, the slab surface, and hypocenters for use as a visualization tool. We present an updated model of the Juan de Fuca slab beneath southern British Columbia, Washington, Oregon, and northern California, and use this model to separate earthquakes occurring above and below the slab surface. en September, 2006 publication date Complete None planned -127.979000 -121.378700 50.003000 39.339800 -127.979000 -121.378700 50.003000 39.339800 102.430000 0.000000 km Thesaurus of Geological terms hypocenter subduction Cascades Juan De Fuca Thesaurus of Geological terms Pacific Northwest DISCLAIMERS This Compact Disc Read-Only Memory (CD-ROM) publication was prepared by an agency of the U.S. Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe on privately owned rights. 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James Luke Blair USGS Manager, Menlo Park Earthquake Hazards Geographic Information Systems laboratory 650-329-4707 650-329-5163 lblair@usgs.gov 9-5 PST Starting hypocenter database from the composite earthquake catalog maintained by ANSS (Advanced National Seismic System) at University of California, Berkeley (http://quake.geo.berkeley.edu/cnss/cnss-catalog.html). Unclassified Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.1.0.722 Shapefile The RMSS value for each point is included in the attribute table for each hypocenter location. Rmss The root-mean-square (RMS) travel time residual, in sec, using all weights. This parameter provides a measure of the fit of the observed arrival times to the predicted arrival times for this location. Smaller numbers reflect a better fit of the data. The value is dependent on the accuracy of the velocity model used to compute the earthquake location, the quality weights assigned to the arrival time data, and the procedure used to locate the earthquake. The RMSS value for each point is included in the attribute table for each hypocenter location. Rmss The root-mean-square (RMS) travel time residual, in sec, using all weights. This parameter provides a measure of the fit of the observed arrival times to the predicted arrival times for this location. Smaller numbers reflect a better fit of the data. The value is dependent on the accuracy of the velocity model used to compute the earthquake location, the quality weights assigned to the arrival time data, and the procedure used to locate the earthquake. ANSS seismic catalog spreadsheet Additional filters were performed after data was downloaded. See report for methodology. USGS Information Services, Box 25286, Denver Federal Center, Denver, CO, 80225 United States Geological Survey Additional filters were performed after data was downloaded. See report for methodology. http://quake.geo.berkeley.edu/anss/catalog-search.html 20031110 11374700 20060920 08595600 20060920 10394200 Vector Entity point 11055 Simple FALSE TRUE FALSE Point 11055 0.000000 0.000000 Decimal degrees D_WGS_1984 WGS_1984 6378137.000000 298.257224 GCS_WGS_1984 0.000001 Explicit elevation coordinate included with horizontal coordinates hypos_below_slab_GCS_wgs84 Hypocenters below the surface of the Juan de Fuca plate at depth 11055 Feature Class FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. 0 FID OID 0 4 Shape Feature geometry. ESRI Coordinates defining the features. 0 Shape Geometry 0 0 Id Id Number 6 EQ_ID_2EQ_ID_2Number10 MAG Hypocenter Magnitude MAG Number 10 SLABCALC Vertical distance in km above or below the slab surface (obtained by adding RASTERVALU and DEPTH values) SLABCALC Number 10 REL_POS Text of hypocenter position (above, below, outside) relative to slab surface REL_POS Number 10 MAG_CAT Simple magnitude categories for scaling hypocenters. Hypocenters with 1-2mag are in category 0. Hypocenters with 2-3mag are in category 1 etc. 11 MAG_CAT Number 19 YEAR Hypocenter Year 11 YEAR Number 19 MONTH Hypocenter Month 11 MONTH Number 19 DAY Hypocenter Day 11 DAY Number 19 HRMN Hypocenter Hours and Minutes HRMN Number 19 11 SECND Hypocenter Seconds 11 SECND Number 19 LAT Latitude in Decimal Degrees LAT Number 10 LONG Longitude in Decimal Degrees LONG Number 19 11 DEPTH Hypocenter Depth in km 11 DEPTH Number 19 NS Number of Stations reporting NS String 254 GAP Azimuthal Gap 8 GAP Number 19 RMS Root Mean Squares 11 RMS Number 19 SOURCE Reporting Source SOURCE String 12 RASTERVALU The depth of the slab surface, referred to sea level, at the XY location of the hypocenter RASTERVALU Number 4 DEPTH_CAT Simple depth categories for shading hypocenters. Hypocenters 10-20km in depth are in category 1. DEPTH_CAT Number 4 Hypocenters downloaded from the ANSS catalog at the internet site: http://quake.geo.berkeley.edu/anss/ Initial Query consisted of: Events occurring between 1/1/1975 to 12/31/2005, Events within 39N to 52N latitude; 120W to 132W longitude, Reporting stations greater than 8, Events of magnitude greater than 1, Events with depth greater than 2 km, Upon download of the data in text format, an AML imported the text file into an ArcInfo coverage and new fields were added to accommodate further calculations and data organization. Further filtering of data included: Events with travel time residual RMS less than or equal to 0.3 sec for regional networks (such as NCSC, PGC, PNSN) or greater were removed. Events with trravel time residual RMS between 0.3 and 1.0 for teleseismic (NEIC) network were removed. (see report for further explanation) Data presented on CD-ROM 0.464 0.464 20061012 James Luke Blair USGS, Earthquake Hazards Team GIS lab manager REQUIRED: The mailing and/or physical address for the organization or individual. REQUIRED: The city of the address. REQUIRED: The state or province of the address. REQUIRED: The ZIP or other postal code of the address. 650-329-4707 lblair@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time en http://www.esri.com/metadata/esriprof80.htmlESRI Metadata Profile Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.1.0.722 -127.979 50.003 39.3398 -121.3787 1 hypos_below_slab_GCS_wgs84 -127.979 50.003 39.3398 -121.3787 1 002 Local Area Network file://\\GISLABPC1\Ticci\McCrory\Web_files\New_Files\BINARY_GIS_DATA\GIS_Data\hypos_below_slab_GCS_wgs84.shp 0.464 Shapefile 20061012 20061012 10161900 20061012 FALSE 10161900 10141000 {D7B9518F-F851-4814-920A-3C5E52B21C08} 20061012 dataset ISO 19115 Geographic Information - Metadata DIS_ESRI1.0 GCS_WGS_1984 11055