Explosion Source Strong Ground Motions in the Mississippi Embayment

Langston, Charles A.; Bodin, Paul; Powell, Christine; Withers, Mitch; Horton, Steve; Mooney, Walter D.

doi:10.1785/0120050105

Cited by 24 publications

(37 citation statements)

References 27 publications

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“…This observation suggests that waves are being scattered by velocity heterogeneity in the embayment. These data were the highest amplitude strong motion data yet recorded in the Mississippi Embayment (LANGSTON et al, 2006). Vertical motions at the stations near each blast attained peak accelerations more than 2 g (LANGSTON et al, 2006) and peak accelerations at the two arrays were roughly 20% g Part of the Mississippi Embayment in Tennessee, Arkansas and Missouri of the Central United States.…”

Section: Array Datamentioning

confidence: 66%

“…4a), and therefore it is a weak ground motion (AKI, 1988). Very close to the blast (*74 m), the acceleration is more than 2 g (LANGSTON et al, 2006) and about 0.2 g at the farthest (*2.65 km) strong motion sensor (Fig. 4b).…”

Section: Nonlinearity From Explosion Data In the Mississippi Embaymentmentioning

confidence: 96%

“…165, 2008 Sediment Nonlinearity (Fig. 2c), not expected from an axysymmetric explosion, is very strong and filled with scattered Rayleigh waves (LANGSTON et al, 2006). Data from these arrays offer a unique opportunity to examine several important attributes of high frequency strong ground motion in the Mississippi Embayment that are expected be useful to seismic engineering design, since there are no comparable strong motion data from natural earthquakes in the area.…”

Section: Array Datamentioning

confidence: 99%

“…2a and b). Following LANGSTON et al's (2006) phases identification, the radial seismogram from the farthest strong motion station was divided into PS wave (0-4 sec), higher-mode Rayleigh waves (5-10 sec), fundamental-mode Rayleigh wave (10-16 sec), and coda (16-22 sec). The Fourier transform of each part of the seismogram is computed using the Seismic Analysis Code (SAC).…”

Section: Resonance Frequency Shift and Amplitude Reductionmentioning

confidence: 99%

“…Arrays of eight strong-motion seismographs were installed 2.5 km from the first explosion and 1.25 km from the second explosion with 15-meters inter-station spacing ( Fig. 1 for blast 1; LANGSTON et al, 2006). Broadband stations in the Mississippi Embayment also recorded weak motions from these blasts.…”

Section: Introductionmentioning

confidence: 99%

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Study of Sediment Nonlinearity Using Explosion Data in the Mississippi Embayment

Jemberie¹

2008

Pure appl. geophys.

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Strong and weak motion data from the Mississippi Embayment Seismic Excitation Experiment (ESEE) were analyzed for signatures of nonlinear site responses. This experiment was performed jointly by the University of Memphis and U. S. Geological Survey in October 2002, by detonating two explosions of 2500 and 5000 lbs. Intrinsic and scattering Q estimates (Q I and Q S ) from the coda of the strong motion data were found to be very low compared to previously determined Q values of P-and Rayleigh waves of weak motion data from the same explosions. The Q I estimates from P-wave late coda of the strong motion data are less by more than 100 at 3 Hz and by more than 200 at 10 Hz, compared to the P-wave Q values determined from the weak motion data by Langston et al (2005). Also, Q I determined from the late coda of strong motion Rayleigh-wave data is less by more than 200 at 0.5 Hz and by more than 50 at 3.0 Hz, compared to Q values determined from Rayleigh-wave weak motion data. A resonance peak spectral amplitude of the early part of a strong motion seismogram is shifted to lower frequencies compared to that from a later part of the same seismogram. Spectral amplitude ratios between transverse and vertical components of the strong motion data are degraded between frequencies 2 and 10 Hz for P waves, and less than 4 Hz for Rayleigh waves compared to the weak motion transverse to vertical spectral ratio. All these are signatures of nonlinear site responses during strong ground motion. This study proves the non-transportability of weak motion attenuation results to estimate ground motion from a future large earthquake that may take place in areas like the New Madrid Seismic zone.

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Section: Array Datamentioning

confidence: 66%

Section: Nonlinearity From Explosion Data In the Mississippi Embaymentmentioning

confidence: 96%

Section: Array Datamentioning

confidence: 99%

Section: Resonance Frequency Shift and Amplitude Reductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of Sediment Nonlinearity Using Explosion Data in the Mississippi Embayment

Jemberie¹

2008

Pure appl. geophys.

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Wave gradiometry and its link with Helmholtz equation solutions applied to USArray in the eastern U.S.

Liu

Holt

2015

JGR Solid Earth

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Wave gradiometry is an array processing technique utilizing the shape of seismic wavefields captured by USArray TA stations to determine fundamental wave propagation characteristics. We first explore a compatibility relation that links the displacement spatial gradients to seismogram displacements and velocities through two unknown coefficients, trueA→ and trueB→. These coefficients are solved for through iterative, damped least squares inversion to provide estimates of phase velocity, back azimuth, radiation pattern, and geometrical spreading. We show that the trueA→ coefficient corresponds to the gradient of logarithmic amplitude, and the trueB→ coefficient corresponds approximately to the local wave slowness. trueA→ and trueB→ vector fields are interpolated to explore a second compatibility relation through solutions to the Helmholtz equation. For most wavefields passing through the eastern U.S., we show that the trueA→ coefficients are generally orthogonal to the trueB→ coefficients. Where they are not completely orthogonal, there is a strong positive correlation between ∇·trueB→ and changes in geometrical spreading, which can be further linked with areas of strong energy focusing and defocusing. We finally obtain isotropic Rayleigh wave phase velocity maps for 15 periods between 20 and 150 s, by stacking results from 37 earthquakes, which show a velocity change along the approximate boundary of the early Paleozoic continental margin. We also observe two low‐velocity anomalies, one centered over the central Appalachians where Eocene basaltic volcanism has occurred and the other within the northeastern U.S., possibly associated with the Great Meteor Hotspot track.

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The shallow elastic structure of the lunar crust: New insights from seismic wavefield gradient analysis

Sollberger

Schmelzbach

Robertsson

et al. 2016

Geophysical Research Letters

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Enigmatic lunar seismograms recorded during the Apollo 17 mission in 1972 have so far precluded the identification of shear‐wave arrivals and hence the construction of a comprehensive elastic model of the shallow lunar subsurface. Here, for the first time, we extract shear‐wave information from the Apollo active seismic data using a novel waveform analysis technique based on spatial seismic wavefield gradients. The star‐like recording geometry of the active seismic experiment lends itself surprisingly well to compute spatial wavefield gradients and rotational ground motion as a function of time. These observables, which are new to seismic exploration in general, allowed us to identify shear waves in the complex lunar seismograms, and to derive a new model of seismic compressional and shear‐wave velocities in the shallow lunar crust, critical to understand its lithology and constitution, and its impact on other geophysical investigations of the Moon's deep interior.

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Explosion Source Strong Ground Motions in the Mississippi Embayment

Cited by 24 publications

References 27 publications

Study of Sediment Nonlinearity Using Explosion Data in the Mississippi Embayment

Study of Sediment Nonlinearity Using Explosion Data in the Mississippi Embayment

Wave gradiometry and its link with Helmholtz equation solutions applied to USArray in the eastern U.S.

The shallow elastic structure of the lunar crust: New insights from seismic wavefield gradient analysis

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