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2-D Path Corrections for Local and Regional Coda Waves: A Test of Transportability

Description: Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. [2003] has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. We will compare performance of 1-D versus 2-D path corrections in a variety of regions. First, the complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Next, we will compare results for the Italian Alps using high frequency data from the University of Genoa. For Northern California, we used the same station and event distribution and compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7 {le} f {le} 8.0-Hz), the …
Date: July 13, 2005
Creator: Mayeda, K M; Malagnini, L; Phillips, W S; Walter, W R; Dreger, D S & Morasca, P
Partner: UNT Libraries Government Documents Department
open access

An 8-Element Fast-Neutron Double-Scatter Directional Detector.

Description: We have constructed a fast-neutron double-scatter spectrometer that efficiently measures the neutron spectrum and direction of a spontaneous fission source. The device consists of two planes of organic scintillators, each having an area of 125 cm{sup 2}, efficiently coupled to photomultipliers. The four scintillators in the front plane are 2 cm thick, giving almost 25% probability of detecting an incident fission-spectrum neutron at 2 MeV by proton recoil and subsequent ionization. The back plane contains four 5-cm-thick scintillators which give a 40% probability of detecting a scattered fast neutron. A recordable double-scatter event occurs when a neutron is detected in both a front plane detector and a back plane detector within an interval of 500 nanoseconds. Each double-scatter event is analyzed to determine the energy deposited in the front plane, the time of flight between detectors, and the energy deposited in the back plane. The scattering angle of each incident neutron is calculated from the ratio of the energy deposited in the first detector to the kinetic energy of the scattered neutron.
Date: July 31, 2005
Creator: Vanier, P. E. & Forman, L.
Partner: UNT Libraries Government Documents Department
open access

103-06A - A6 - Base Input - Army - Rock Island Arsenal - IL

Description: Base Input - Army - Rock Island Arsenal - IL - Includes: Itinerary for the visit of Mr. Samuel K. Skinner; List of attendees; PowerPoint presentation of BRAC Recommendations and Possible Changes prepared by Mr. Alan Wilson, Garrison Manager; and Rock Island Arsenal brochure.
Date: July 1, 2005
Creator: United States. Defense Base Closure and Realignment Commission.
Partner: UNT Libraries Government Documents Department
open access

103-06A - A6 - Base Input - Army - Rock Island Arsenal IL - Mr. Samuel K. Skinner - US Army Garrison - Rock Island Arsenal - Installation Overview Briefing

Description: Base Input - Army - Rock Island Arsenal IL - Mr. Samuel K. Skinner - US Army Garrison - Rock Island Arsenal - Installation Overview Briefing - PowerPoint Presentation made by Mr. Alan Wilson, Garrison Manager
Date: July 1, 2005
Partner: UNT Libraries Government Documents Department
open access

103-06A-AF20 - Base Input - Air Force - Elmendorf Air Force Base/Kulis Air Guard Station/Eielson Air Force Base - AK

Description: Base Input - Air Force - Elmendorf Air Force Base/Kulis Air Guard Station/Eielson Air Force Base - AK - Mr. Small BRAC Commission Visit - Includes: Powerpoint presentation from Lt. Col Pat McCrea; Eielson Air Force Base ALASKA Home of the Iceman Team Powerpoint Presentation; Welcome to the 176th Wing Kulis Air National Guard Base Alaska Report; biographies; Welcome to the 176th Wing Presentation
Date: July 1, 2005
Creator: United States. Defense Base Closure and Realignment Commission.
Partner: UNT Libraries Government Documents Department
open access

103-06A-RH11 - State Input - VA - Regional Hearing 07-7-05 - National Capital Area

Description: While we in Congress retain a right to review and reject the final recommendations in total, the commission is charged with reviewing and amending each recommendation to ensure the use of correct data, an accurate and substantiated assessment of cost savings, and---most importantly recommendations that advance the tenets of "military value" as clearly prescribed in law.
Date: July 19, 2005
Creator: United States. Defense Base Closure and Realignment Commission.
Partner: UNT Libraries Government Documents Department
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