Upper Mississippi embayment shallow seismic velocities measured in situ

Liu, Hsi‐Ping; Hu, Yiguang; Dorman, James; Chang, Tzyy-Shiou; Chiu, Jer‐Ming

doi:10.1016/s0013-7952(97)00009-4

Cited by 35 publications

(35 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the constraints on velocity by the Wilson 2-14 acoustic well log, observation of reverberation phases within the P and S waveforms, and the change in character of P and S waveforms between seismic stations all point to significant near-surface wave propagation effects that shape body-wave phases in the time and frequency domains. These observations are consistent with the variation of near-surface P-and S-wave velocities seen in detailed VSP well logs (Liu et al, 1997), refraction studies (Street et al, 2001), surface wave dispersion studies (Romero and Rix, 2001;Rix et al, 2002), and geotechnical studies (Schneider et al, 2001).…”

Section: Discussionsupporting

confidence: 82%

“…Acoustic well logs are available that show considerable heterogeneity with depth (discussed later) but with average P-wave velocities of 1.8-2.5 km/sec within the section. Notably, there have been no direct measurements of S-wave velocity over the section, although Liu et al (1997) produced a detailed look of the upper 70 m of the sediment using a vertical seismic profiling (VSP) technique. Also, Dorman and Smalley (1994) estimated the S-wave velocity from Rayleigh-wave dispersion from a local earthquake.…”

Section: Velocity Structure and Anelastic Attenuation In The Mississimentioning

confidence: 99%

“…The well logs are deficient in describing structure near the free surface since each well was cased in this region. Liu et al (1997) provided some valuable insight on the nature of the nearsurface structure through VSP logging of shallow boreholes at two sites within the embayment. Figure 11 shows the Pand S-wave velocity structures determined by these investigators and the expected P-and SV-wave responses.…”

Section: Effect Of 1d Heterogeneity In Mississippi Embayment Sedimentsmentioning

confidence: 99%

“…It is very likely that there are significant density changes . Velocity models obtained by Liu et al (1997) using VSP techniques.…”

Section: Inferred Site Structurementioning

confidence: 99%

See 3 more Smart Citations

Local Earthquake Wave Propagation through Mississippi Embayment Sediments, Part I: Body-Wave Phases and Local Site Responses

Langston

2003

Bulletin of the Seismological Society of America

View full text Add to dashboard Cite

P and S body waves from microearthquakes in the New Madrid Seismic Zone (NMSZ) are investigated at selected sites in an effort to understand wave propagation from future large earthquakes. Earthquake body waveforms display distinctive features that constrain the nature of P-and S-wave local site responses and wave propagation within the unconsolidated Mississippi embayment sediments. Modeling of the waveforms demonstrates that a near-surface low-velocity zone is characteristic of structure within the upper 60 m of the sedimentary column and produces large Pand S-wave resonance effects that can be used to infer near-site conditions. Site resonance effects change because of velocity heterogeneity between individual receivers but imply that embayment sediments will substantially amplify ground motions at high frequencies. Site resonance affects P-and S-wave amplitude spectra and can bias estimates of source and anelastic attenuation parameters. Travel times of observed body-wave phases such as P, PpPhp (the first P-wave reverberation within the entire sedimentary column), Ps, Sp, S, and SsPhp can be used to estimate the average wave slownesses and Poisson's ratio within the embayment sediments; an average Poisson's ratio of 0.44 is obtained for the central NMSZ under station PEBM. Detailed S-wave velocities are derived for a Nafe-Drake sediment model using acoustic well logs and the travel-time constraints of observed seismic phases. V p /V s ratios vary from 5.5 near the surface to approximately 2.4 at the base of the sediments. Use of the well-log data in wave calculations also explains much of the nature of P-and S-wave coda within the waveforms and shows that 1D heterogeneity is a first-order influence on seismic-wave propagation within the Mississippi embayment.

show abstract

Section: Discussionsupporting

confidence: 82%

Section: Velocity Structure and Anelastic Attenuation In The Mississimentioning

confidence: 99%

Section: Effect Of 1d Heterogeneity In Mississippi Embayment Sedimentsmentioning

confidence: 99%

“…It is very likely that there are significant density changes . Velocity models obtained by Liu et al (1997) using VSP techniques.…”

Section: Inferred Site Structurementioning

confidence: 99%

See 2 more Smart Citations

Local Earthquake Wave Propagation through Mississippi Embayment Sediments, Part I: Body-Wave Phases and Local Site Responses

Langston

2003

Bulletin of the Seismological Society of America

View full text Add to dashboard Cite

show abstract

“…Solid squares show the available local climatic stations for temperature data used in table 2. Triangles represent locations of three shallow boreholes used in Liu et al (1997) to perform down-hole vertical seismic profiling.…”

Section: Ting-l Lin and Charles A Langstonmentioning

confidence: 99%