Shear-wave velocity of the sedimentary basin in the upper Mississippi embayment using S-to-P converted waves

1996 ◽  
Vol 86 (3) ◽  
pp. 848-856
Author(s):  
Kou-Cheng Chen ◽  
Jer-Ming Chiu ◽  
Yung-Tun Yang
Keyword(s):  
Travel Time ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Sedimentary Basin ◽  
Vertical Component ◽  
Seismic Zone ◽  
Mississippi Embayment ◽  
Upper Mississippi Embayment ◽  
Converted Waves

Abstract From mid-October 1989 to August 1992, 40 three-component PANDA (Portable Array for Numerical Data Acquisition) stations were deployed in the central New Madrid seismic zone. Three-component digital seismograms recorded by the PANDA stations in the region are characterized by (1) the very weak direct S arrivals on the vertical component, which can be identified unambiguously from the two horizontal components, and (2) at least two prominent secondary arrivals between the direct P and S arrivals, one (Sp) dominant on the vertical component and another (Ps) with smaller amplitude on the two horizontal components. Travel-time differences between the Sp and S and between the P and Ps are the same for different earthquakes recorded at the same station but are different at different stations even for the same event. Polarization analyses of three-component seismograms and travel-time measurements confirm the interpretation that these two secondary arrivals are the P-to-S (Ps) and S-to-P (Sp) converted waves that occur at the bottom of the sedimentary basin beneath each station. Since abundant well-log data are available in the upper Mississippi embayment, the thickness of the sediments beneath each seismic station can be estimated. Travel-time differences between the direct and the converted waves can be used to calculate average shear-wave velocity for the sediments beneath each station. The estimated shear-wave velocities of the sediments beneath PANDA stations vary from 0.45 to 0.67 km/sec. The higher shear-wave velocity associated with thicker sediments can be interpreted as a consequence of increasing compaction of unconsolidated sediments due to increasing overburden.

Qp-Qs relations in the sedimentary basin of the upper Mississippi Embayment using converted phases

1994 ◽  
Vol 84 (6) ◽  
pp. 1861-1868
Author(s):  
Kou-Cheng Chen ◽  
Jer-Ming Chiu ◽  
Yung-Tun Yang
Keyword(s):  
Sedimentary Basin ◽  
Vertical Component ◽  
Spectral Ratio ◽  
Unconsolidated Sediments ◽  
Ratio Method ◽  
Seismic Zone ◽  
Frequency Content ◽  
S Wave ◽  
Mississippi Embayment ◽  
Upper Mississippi Embayment

Abstract Three-component digital seismograms recorded by the 40 PANDA (Portable Array for Numerical Data Acquisition) stations in the New Madrid seismic zone were analyzed to study seismic wave attenuation in the sedimentary basin using the spectral ratio method. A prominent S-to-P (Sp) converted phase was generated at the boundary between the uppermost sedimentary basin and the underlying Paleozoic rocks. The direct S wave on the horizontal component is characterized by a lower-frequency content than that of the converted Sp wave on the vertical component. The differences in frequency content between the direct S and the Sp converted waves can be attributed to the different attenuation effects between P and S waves in the unconsolidated sediments. The spectral ratio between the low-frequency S wave and the high-frequency converted Sp wave from the bottom of the sediments can be used to yield a relationship between Qp and Qs in the sediments. Results from PANDA stations with well-constrained spectral ratios in the frequency range from 2 to 25 Hz give the Qp value ranging from 25 to 60 and Qs from 25 to 30 for the sedimentary basin in the upper Mississippi Embayment.

Deep Shear Wave Velocity Profiles from Surface Wave Measurements in the Mississippi Embayment

2007 ◽  
Vol 23 (4) ◽  
pp. 791-808 ◽  
Author(s):  
Brent L. Rosenblad ◽  
Jianhua Li ◽  
Farn-Yuh Menq ◽  
Kenneth H. Stokoe
Keyword(s):  
Surface Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Response ◽  
Source Surface ◽  
Mississippi Embayment ◽  
Near Surface ◽  
Wave Measurements ◽  
Central United States

Shear wave velocity ( VS) profiles to depths of approximately 200 m were developed from active-source surface wave velocity measurements in the Mississippi Embayment region of the Central United States. Soil deposits in this region are hundreds of meters thick, but are poorly characterized at depths below 60 m. Measurements were performed at five locations in Arkansas and Tennessee with a maximum distance between sites of approximately 130 km. The median VS profile calculated from the five profiles is in good agreement with a generic reference VS profile for the Mississippi Embayment that has been used in recent site response studies. The near-surface VS profiles at the five sites were remarkably consistent with average shear wave velocities in the top 30 m ( VS30), varying by less than 10%. Increasing variability between the VS profiles was observed at greater depths. The variability between VS profiles was shown to be correlated with changes in lithology at two of the sites where nearby lithologic information was available.

Transportation Routes in Soils Susceptible to Ground Failure: New Madrid Seismic Zone

2000 ◽  
Vol 1736 (1) ◽  
pp. 127-133
Author(s):  
Salome Romero ◽  
Glenn J. Rix ◽  
Steven P. French
Keyword(s):  
Remote Sensing ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Data Sources ◽  
New Madrid Seismic Zone ◽  
Seismic Zone ◽  
Remote Sensing Imagery ◽  
Geologic Maps ◽  
Transportation Routes

Geologic deposits susceptible to ground motion amplification under seismic loading in the New Madrid Seismic Zone are delineated using multiple data sources including in situ measurements, geologic maps, and remote-sensing imagery. Soils are classified on the basis of the recommendations from the National Earthquake Hazards Reduction Program, which recommends a classification based on the average shear wave velocity of the geologic material in the upper 30 m. Measurements of shear wave velocity were obtained from Central United States Earthquake Consortium state geologists, the U.S. Geological Survey, and several researchers. However, since this is a predominantly rural area, limited field test data are available. Therefore, several other data sources are introduced including geologic maps and remote-sensing imagery to extrapolate dynamic properties in areas lacking extensive field measurements. Each data source was incorporated into a geographic information system for subsequent analysis. Bridges susceptible to failure from amplification of seismic waves and located on key transportation routes are identified for subsequent risk assessment or seismic retrofitting since the performance of these structures affects disaster planning and rescue efforts and may have severe consequences for the national economy.

Crustal and lithospheric architecture of the Gulf of Mexico and its continental margins from ambient noise Rayleigh wave tomography

2021 ◽  
Author(s):  
Luan C. Nguyen ◽  
Alan Levander ◽  
Fenglin Niu ◽  
Guoliang Li
Keyword(s):  
Gulf Of Mexico ◽  
Rayleigh Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Ambient Noise ◽  
Vertical Component ◽  
Continental Margins ◽  
Continental Lithosphere ◽  
Short Period

<p>The Gulf of Mexico formed as a result of continental breakup between the North and SouthAmerican plates and a short period of seafloor spreading in the Late Jurassic-Early Cretaceous. This small ocean basin offers an opportunity to further our understanding of continental rifting processes and the geologic evolution of continental margins during and after rifting. However, previous knowledge of lithospheric structure has been limited to crustal investigations. We constructed a 3D shear-wave velocity model for the Gulf of Mexico region using cross-correlations of the ambient noise field and measurement of vertical component Rayleigh wave phase velocities in the period band 15 to 95 s. We employed continuous data recorded by more than 500 stations in seismic networks in the US, Mexico and Cuba. Our model shows distinct variation in lithospheric structures that reliably identify and constrain the properties of extended continental and oceanic domains. We estimate the depth of the lithosphere-asthenosphere boundary to be in the range of 85-100 km with the thinnest lithosphere under the oceanic region. A low velocity zone is observed below the lithosphere centered at ~150 km depth with a minimum shear-wave velocity of ~4.45 km/s. Lithospheric mantle underlying the offshore Texas Gulf Coast between oceanic lithosphere and unextended continental lithosphere is characterized by reduced shear-wave velocity. This might indicate that extension resulted in permanent deformation of the continental lithosphere. The differential thinning between the crystalline crust and mantle lithosphere suggests that the extended continental lithosphere has cooled and thickened by approximately 30 km since breakup.</p>

scholarly journals Near surface shear wave velocity in Bucharest, Romania

2008 ◽  
Vol 8 (6) ◽  
pp. 1299-1307 ◽  
Author(s):  
M. von Steht ◽  
B. Jaskolla ◽  
J. R. R. Ritter
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Compressional Wave ◽  
Seismic Zone ◽  
Surface Shear ◽  
Near Surface ◽  
Surface Shear Wave

Abstract. Bucharest, the capital of Romania with nearly 2 1/2 million inhabitants, is endangered by the strong earthquakes in the Vrancea seismic zone. To obtain information on the near surface shear-wave velocity Vs structure and to improve the available microzonations we conducted seismic refraction measurements in two parks of the city. There the shallow Vs structure is determined along five profiles, and the compressional-wave velocity (Vp) structure is obtained along one profile. Although the amount of data collected is limited, they offer a reasonable idea about the seismic velocity distribution in these two locations. This knowledge is useful for a city like Bucharest where seismic velocity information so far is sparse and poorly documented. Using sledge-hammer blows on a steel plate and a 24-channel recording unit, we observe clear shear-wave arrivals in a very noisy environment up to a distance of 300 m from the source. The Vp model along profile 1 can be correlated with the known near surface sedimentary layers. Vp increases from 320 m/s near the surface to 1280 m/s above 55–65 m depth. The Vs models along all five profiles are characterized by low Vs (<350 m/s) in the upper 60 m depth and a maximum Vs of about 1000 m/s below this depth. In the upper 30 m the average Vs30 varies from 210 m/s to 290 m/s. The Vp-Vs relations lead to a high Poisson's ratio of 0.45–0.49 in the upper ~60 m depth, which is an indication for water-saturated clayey sediments. Such ground conditions may severely influence the ground motion during strong Vrancea earthquakes.

Flat Dilatometer (DMT), Cone Penetrometer (CPT) and Seismic Cone (SCPT) Evaluation of Select New Madrid Liquefaction Sites

1992 ◽  
Vol 63 (3) ◽  
pp. 357-366
Author(s):  
Roman D. Hryciw
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Horizontal Stress ◽  
Stress Index ◽  
Seismic Zone ◽  
Cone Penetration ◽  
Seismic Shear ◽  
Tip Resistance ◽  
New Madrid

Abstract Cone Penetration (CPT), Flat Dilatometer (DMT) and Seismic Shear Wave Velocity tests were conducted in four regions of the New Madrid seismic zone. Test results are compared to existing liquefaction criteria and to surface evidence of liquefaction (sandblows) during the 1811–1812 events. In general, all three tests confirm the presence of liquefaction-prone strata at locations with evidence of liquefaction. A “sand blow index” (SBI), which accounts for both local and regional sand blow intensity, correlates reasonably well against the minimum values of DMT horizontal stress index, the normalized CPT tip resistance, and the normalized shear wave velocity at each test location. An upperstratum clay also appears to play a significant role in inhibiting sand blow formation. Its thickness also correlates well with the SBI.

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