Anomalous surface waves from Lop Nor nuclear explosions: Observations and numerical modeling

Surface waves from the Chinese test site of Lop Nor are analyzed using long-period and broadband stations located at regional and teleseismic distances and at different azimuths. For most azimuths, strong Love waves between 0.02 and 0.045 Hz are observed with an amplitude of up to 10 times that of the Rayleigh waves. In addition, an anomalous early Rayleigh wave train is observed at some stations in western Europe. Due to a particularly favorable station and source configuration, it is possible to isolate the areas where the anomalies are created. The high-amplitude Love waves must be attributed to either source effects or path effects immediately north of Lop Nor. The early wave train is shown to be due to a partial energy conversion between Love and Rayleigh waves, probably at the Tornquist Zone. To estimate the possible contribution from surface wave conversions to the observed anomalies, numerical simulations are carried out with the indirect boundary element method. The simulations show that a relatively small variation of crustal thickness can induce Rayleigh to Love wave conversions between 0.02 and 0.1 Hz frequency. The calculated amplitudes of the Love waves are significant (up to 35% of the amplitude of the incoming Rayleigh waves), but they are too small to fit the observed amplitude anomaly. The observed converted waves and the numerical results nevertheless indicate that surface wave conversions can be significant across strong lateral crustal heterogeneities. In particular, the conversions due to changes in crustal thickness are located in the period interval which is routinely used for estimation of Ms

Resonant conditions for Love wave guiding layer thickness

In this work we report a systematic investigation of polymer overlayer thickness in a Love wave device working at a fundamental frequency of 110MHz and at the 330MHz harmonic. At both frequencies we observe the initial reduction in insertion loss associated with a Love wave device. Significantly, we also observe a series of resonant conditions as the layer thickness is further increased. The separation of these resonances is attributed to an increase in thickness of half of the acoustic wavelength in the polymer

SU-8 Guiding Layer for Love Wave Devices

SU-8 is a technologically important photoresist used extensively for the fabrication of microfluidics and MEMS, allowing high aspect ratio structures to be produced. In this work we report the use of SU-8 as a Love wave sensor guiding layer which allows the possibility of integrating a guiding layer with flow cell during fabrication. Devices were fabricated on ST-cut quartz substrates with a single-single finger design such that a surface skimming bulk wave (SSBW) at 97.4 MHz was excited. SU-8 polymer layers were successively built up by spin coating and spectra recorded at each stage; showing a frequency decrease with increasing guiding layer thickness. The insertion loss and frequency dependence as a function of guiding layer thickness was investigated over the first Love wave mode. Mass loading sensitivity of the resultant Love wave devices was investigated by deposition of multiple gold layers. Liquid sensing using these devices was also demonstrated; water-glycerol mixtures were used to demonstrate sensing of density-viscosity and the physical adsorption and removal of protein was also assessed using albumin and fibrinogen as model proteins

ST Quartz Acoustic Wave Sensors with Sectional Guiding Layers

We report the effect of removing a section of guiding layer from the propagation paths of ST-quartz Love wave sensors; this offers the ease of fabrication of a polymer guiding layer whilst retaining the native surface of the quartz which may then be used for the attachment of a sensitizing layer. Data is presented for rigid and viscous loading, which indicates a small reduction in mass sensitivity compared to a Love wave device. Biosensing capabilities of these discontinuous ‘sectional’ guiding layer devices are demonstrated using protein adsorption from solution

A wave near the edge of a circular disk

It is shown that in the Love-Kirchhoff plate theory, an edge wave can travel in a circular thin disk made of an isotropic elastic material. This disk edge wave turns out to be faster than the classic flexural acoustic wave in a straight-edged, semi-infinite, thin plate, a wave which it mimics when the curvature radius becomes very large compared to the wavelength

Relativistic theory of tidal Love numbers

In Newtonian gravitational theory, a tidal Love number relates the mass multipole moment created by tidal forces on a spherical body to the applied tidal field. The Love number is dimensionless, and it encodes information about the body's internal structure. We present a relativistic theory of Love numbers, which applies to compact bodies with strong internal gravities; the theory extends and completes a recent work by Flanagan and Hinderer, which revealed that the tidal Love number of a neutron star can be measured by Earth-based gravitational-wave detectors. We consider a spherical body deformed by an external tidal field, and provide precise and meaningful definitions for electric-type and magnetic-type Love numbers; and these are computed for polytropic equations of state. The theory applies to black holes as well, and we find that the relativistic Love numbers of a nonrotating black hole are all zero.Comment: 25 pages, 8 figures, many tables; final version to be published in Physical Review

Harmonic Love wave devices for biosensing applications

Simultaneous operation of a Love wave biosensor at the fundamental frequency and third harmonic, including the optimisation of IDT metallisation thickness, has been investigated. Data is presented showing a sequence of deposition and removal of a model mass layer of palmitoyl-oleoyl-sn-glycerophosphocholine (POPC) vesicles while frequency hopping between 110 and 330 MH

Master of Science

thesisThis thesis examines the feasibility of inverting surface waves in common shot point (CSP) scismic data for S- and P-wave velocities. Several approaches to surface wave inversion are examined: 1) separate Love and Rayleigh wave inversions for S- and P-wave velocities; 2) Love wave inversion for S-wave velocities that is then followed by Rayleigh wave inversion for S- and P-wave velocities; and 3) Love wave inversion for S-wave velocities that are then used in Rayleigh wave inversion for P-wave velocities. Inversion of synthetic data suggests that a combination of Love and Rayleigh wave inversion will provide the best results, especially if the Love waves are first used to reconstruct the S-wave velocities and the Rayleigh waves are then used to recover the P-wave velocities. Results also suggest that S-wave velocities inverted from Love waves may be more reliable than those from Rayleigh wave inversion, and that combining Love and Rayleigh wave inversion will provide the most accurate S-wave velocity reconstruction from field data. Density determination appears impractical using surface wave inversion. To verify the practicality of surface wave inversion, a nine-component surface wave experiment was performed in northeast Texas (courtesy of Arco Research). Tau-p and Fourier transforms are applied to the YY (cross-line component source recorded on cross-line component gcophones) and ZZ (z-component source recorded on z-component geophones) CSP gathers to recover Love and Rayleigh wave dispersion curves respectively. These curves show clearly the fundamental and higher harmonic modes from about 2 Hz to 14 Hz. Inversion of the fundamental mode data suggests shear velocities of 180 m/s near the surface with an abrupt change to 400 m/s within the first 10 meters followed by a gradual increase to 650 m/s at a depth of 65 meters. This is in good agreement with the shear velocities measured from vertical seismic profile (VSP) data. Results suggest that either Love or Rayleigh wave inversion can be used to provide shear wave statics and near-surface layer velocities, but that a combination of the two can improve the reliability of the velocity reconstruction