Measuring and Modeling of P- and S-Wave Velocities on Crustal Rocks: A Key for the Interpretation of Seismic Reflection and Refraction Data

Abstract

Lithologic interpretations of the earth crust from seismic wave velocities are non-unique so that inferences about composition can not be drawn. In order to evaluate how elastic properties of rock materials are controlled by lithology at in situ pressures and temperatures, compressional (Vp), shear wave velocities (Vs) and velocity anisotropy of crustal rocks were measured at conditions of greater depth. The first part deals with the interdependence of elastic wave propagation and the physical and lithological parameters. In the second part data from laboratory seismic measurements and theoretical calculations are used to interpret (1) a shallow seismic reflection line (SE Finland) and (2) a refraction profile of a deep crust (Central China). The comparison of the calculated velocities with the experimentally-derived in situ velocities of the Finnish crustal rocks give hints that microcracks have an important bearing on the in situ seismic velocities, velocity anisotropy and the reflectivity observed at relative shallow depth. The coupling of the experimentally-derived in situ velocities of P-and S-wave and corresponding Poisson's ratios of relevant exhumed high-grade metamorphic crustal rocks from Central China with respective data from seismic refraction profiling provided a key for the lithologic interpretation of a deep seismic crustal structure.

Effect of fluid H2O on compressional wave velocities in quartz aggregate up to 500°C at 0.5 GPa

“…The pressure derivative (in the range P = 0.3 to 0.6 GPa) was then used to linearly extrapolate the velocity data, which yielded a Vp value of 6.04 km s −1 under ambient conditions. This is the so-called intrinsic velocity of Kern (2011). As in previous studies (Shingai et al 2001;Kitamura et al 2003;Kono et al 2004;Nishimoto et al 2005;Ishikawa et al 2008), linear trends of velocity as a function of pressure were observed above a threshold pressure of between 0.3 and 0.6 GPa.…”

Crustal Shear Wave Velocity Structure of Central Idaho and Eastern Oregon From Ambient Seismic Noise: Results From the IDOR Project

“…The Poisson's ratios, , in Table 1 are similar to those reported in seismic studies-both laboratory and field based-of continental lithologies (Christensen, 1996;Holbrook et al, 1999;Kern, 2011;Lombardi et al, 2008;Miller & Christensen, 1994). However, the shallow to midcrustal depth V p ∕V s ratios we calculate are consistently higher than the V p ∕V s ( values, from the h-method of Zhu & Kanamori, 2000) determined by Stanciu et al (2016) for the IDOR area.…”

Effect of small-scale heterogeneities on interpretation of crustal compositions exemplified by a layered anorthosite

“…Fountain et al, 1994;Ji et al, 1997). In addition to poor lateral resolution, the detection of heterogeneities in the lower crust may be difficult due to the non-unique lithological interpretation of lower crustal rocks from seismic velocities since a variety of rock type mixtures can yield the same velocities (Kuusisto et al, 2006;Kern, 2011). Additional constraints can be established if the seismic data are correlated with experimentally determined or calculated P-and S-wave velocities at lower crustal conditions for rock samples collected from surface outcrops or from xenoliths (Christensen and Wepfer, 1989;Jackson et al, 1990;Kern et al, 1999;Kuusisto et al, 2006;Kern, 2011).…”