Explosion Source Strong Ground Motions in the Mississippi Embayment

• DOI: 10.1785/0120050105
• Publication Date: 2006-05-31T07:59:55Z
• Authors: C. A. Langston
• Keywords: 01 natural sciences; 0105 earth and related environmental sciences

Two strong-motion arrays were deployed for the October 2002 Embay- ment Seismic Excitation Experiment to study spatial variation of strong ground motions in deep, unconsolidated sediments Mississippi embayment because there are no comparable data from natural earthquakes area. Each linear array consisted eight three-component K2 accelerographs spaced 15 m apart situated 1.2 and 2.5 km 2268-kg 1134-kg borehole explosion sources, respectively. The show distinct body-wave surface-wave arrivals that propagate within thick, sedimentary column, high-velocity basement rocks, small-scale structure near surface. Time-domain coherence is computed acceleration, velocity, displacement time windows. Coherence high relatively low-frequency vertical- component Rayleigh waves high-frequency P propagating across ar- ray. Prominent PS conversions seen on radial components, a proxy direct S wave earthquake lose quickly over 105-m length array. Transverse signals least coherent any motion appear be highly scattered. Horizontal phase velocity com- puted by using ratio particle estimates strain based plane-wave-propagation model. resulting time-dependent phase-velocity map useful way infer propagation mechanisms individual seismic phases windows waveforms. Displacement gradient analysis complementary technique processing general spatial-array obtain hori- zontal slowness information.