Source and Path Calibration in Regions of Poor Crustal Propagation using Temporary, Large-Aperture, High-Resolution Seismic Arrays

• Main Authors: Nabelek, John L, Braunmiller, Jochen, Phillips, W S
• Format: Report
• Language: English
• Subjects: APERTURES; BROADBAND; CALIBRATION; CHINA; CLUSTERING; DETECTION; EARTH CRUST; GROUND TRUTH; HIGH RESOLUTION; IRAN; MOMENT TENSORS; MOMENTS; MONITORING; NEPAL; PATHS; PE62601F; PROPAGATION; REPRINTS; SEISMIC ARRAYS; SEISMIC CODA; SEISMIC DATA; SEISMIC EVENTS; Seismology; SOURCES; SYMPOSIA; TENSORS; THREE DIMENSIONAL; TIBET; TWO DIMENSIONAL; VELOCITY; WUAFRL1010SMA1

Broadband seismic data acquired during the Hi-CLIMB field experiment are used to study seismic events and path propagation in the Nepal Himalaya and south-central Tibetan Plateau. Similarities in regional propagation between Tibet and Iran motivate this new study. The 2002-2005 Hi-CLIMB experiment consisted of 233 stations distributed along a dense 800 km linear north-south array extending from the Himalayan foreland into the central Tibetan Plateau. The main array was flanked by a 350 km x 350 km sub-array in southern Tibet and central and eastern Nepal. Our dataset provides an opportunity to obtain seismic event locations for ground truth (GT) evaluation, with Q emphasis on depth, to determine source parameters, and to study distance evolution of seismic coda for yield estimation in low Q regions. Event detection and preliminary automatic location analysis show tens of thousands, otherwise undetected, local seismic events. We will obtain high-quality event locations from manual P- and S-wave picks by joint inversion for location and 2D and 3D velocity structure. We will also perform relative locations to resolve spatial relations of several highly active event clusters. Besides GT-compatibility, high-quality locations are essential for the source parameter and coda evolution portions of the study. We will perform moment tensor Q inversions in a wide magnitude range (1.5 Mw 6), paying particular attention to event depth and size. Full waveform moment-tensor depth is important for validating travel time-derived depth; seismic moment calibrates spectral coda levels and local and regional magnitudes. The dense station spacing of the Hi-CLIMB array is unique for any highly attenuating crustal path region, permitting fine-scale analysis of decay properties for multiple coda types, which is a globally important, unresolved issue in monitoring research. Presented at the conference on Monitoring Research Review 2009 (MRR-2009): Ground-Based Nuclear Explosion Monitoring Technologies, held in Tucson, AZ, on 21-23 Sep 2009. Published in the proceedings of the conference, v1 p158-165, 2009. Prepared in cooperation with Los Alamos National Laboratory (LANL). Sponsored in part by the National Nuclear Security Administration (NNSA). The original document contains color images. All DTIC reproductions will be in black and white.