The effect of oceanic sediments on surface-wave propagation

1975 ◽  
Vol 65 (6) ◽  
pp. 1531-1552
Author(s):  
Donald J. Weidner
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Rayleigh Waves ◽  
Propagation Path ◽  
Surface Wave Propagation ◽  
Oceanic Surface ◽  
Oceanic Sediments ◽  
Wave Phase Velocity ◽  
Short Period ◽  
Mid Atlantic Ridge

abstract Several characteristics of oceanic surface waves can be altered by the presence of low rigidity sediments along the propagation path. Love and Rayleigh waves from mid-Atlantic ridge earthquakes bear many effects of oceanic sediments. The general absence of these surface waves for periods shorter than about 15 sec can be attributed to either attenuation or scattering in thin sediments. Thin sediments also disperse short-period Love waves. Sediments whose thickness exceeds about 2 km are responsible for removing surface-wave energy with periods up to 40 sec. These sediments also alter the particle motion of Rayleigh waves and are responsible for a complicated dispersion relation. These thick sediments substantially reduce the surface-wave phase velocity at periods in excess of 100 sec.

On the nature of oceanic seismic surface waves with predominant periods of 6 to 8 seconds

1961 ◽  
Vol 51 (3) ◽  
pp. 437-455
Author(s):  
Jack Oliver ◽  
James Dorman
Keyword(s):  
Surface Waves ◽  
Deep Sea ◽  
Rayleigh Waves ◽  
Seismic Refraction ◽  
Normal Modes ◽  
Quantitative Agreement ◽  
Period Range ◽  
Oceanic Surface ◽  
Short Period ◽  
Seismic Surface Waves

Abstract The train of normally-dispersed, short-period, oceanic surface waves, commonly identified by the near-sinusoidal nature of all three components of ground motion in the period range of about 6 to 8 seconds, is shown to correspond to propagation in the first Love and first shear normal modes. Theoretical dispersion curves which agree with the observed dispersion of these short-period waves, as well as with dispersion of Rayleigh waves and Love waves of longer periods, are obtained for layered models of the oceanic crust which are consistent with results of seismic refraction studies. In order to obtain good quantitative agreement between theory and observation, it is essential that the effect of the small but finite rigidity of the deep-sea sedimentary layer be included in the calculations.

Estimates of Surface Waves Using Subsurface EM-APEX Floats under Typhoon Fanapi 2010

2018 ◽  
Vol 35 (5) ◽  
pp. 1053-1075 ◽  
Author(s):  
Je-Yuan Hsu ◽  
Ren-Chieh Lien ◽  
Eric A. D’Asaro ◽  
Thomas B. Sanford
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Wave Spectrum ◽  
Nonlinear Least Squares ◽  
Peak Frequency ◽  
Wave Propagation Direction ◽  
Model Studies ◽  
Surface Wave Propagation ◽  
Left Quadrant ◽  
Field Inclination

AbstractSeven subsurface Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats measured the voltage induced by the motional induction of seawater under Typhoon Fanapi in 2010. Measurements were processed to estimate high-frequency oceanic velocity variance associated with surface waves. Surface wave peak frequency fp and significant wave height Hs are estimated by a nonlinear least squares fitting to , assuming a broadband JONSWAP surface wave spectrum. The Hs is further corrected for the effects of float rotation, Earth’s geomagnetic field inclination, and surface wave propagation direction. The fp is 0.08–0.10 Hz, with the maximum fp of 0.10 Hz in the rear-left quadrant of Fanapi, which is ~0.02 Hz higher than in the rear-right quadrant. The Hs is 6–12 m, with the maximum in the rear sector of Fanapi. Comparing the estimated fp and Hs with those assuming a single dominant surface wave yields differences of more than 0.02 Hz and 4 m, respectively. The surface waves under Fanapi simulated in the WAVEWATCH III (ww3) model are used to assess and compare to float estimates. Differences in the surface wave spectra of JONSWAP and ww3 yield uncertainties of <5% outside Fanapi’s eyewall and >10% within the eyewall. The estimated fp is 10% less than the simulated before the passage of Fanapi’s eye and 20% less after eye passage. Most differences between Hs and simulated are <2 m except those in the rear-left quadrant of Fanapi, which are ~5 m. Surface wave estimates are important for guiding future model studies of tropical cyclone wave–ocean interactions.

Short-period seismic noise

1967 ◽  
Vol 57 (1) ◽  
pp. 55-81
Author(s):  
E. J. Douze
Keyword(s):  
Surface Waves ◽  
Rayleigh Waves ◽  
Seismic Noise ◽  
Body Waves ◽  
Deep Hole ◽  
Period Range ◽  
Short Period ◽  
The Subject ◽  
Hole Arrays

abstract This report consists of a summary of the studies conducted on the subject of short-period (6.0-0.3 sec period) noise over a period of approximately three years. Information from deep-hole and surface arrays was used in an attempt to determine the types of waves of which the noise is composed. The theoretical behavior of higher-mode Rayleigh waves and of body waves as measured by surface and deep-hole arrays is described. Both surface and body waves are shown to exist in the noise. Surface waves generally predominate at the longer periods (of the period range discussed) while body waves appear at the shorter periods at quiet sites. Not all the data could be interpreted to define the wave types present.

scholarly journals Automated detection and association of surface waves

1994 ◽  
Vol 37 (3) ◽  
Author(s):  
R. G. North ◽  
C. R. D. Woodgold
Keyword(s):  
Surface Waves ◽  
Group Velocity ◽  
Rayleigh Waves ◽  
Arrival Time ◽  
Narrow Band ◽  
Broad Band ◽  
Detection Algorithm ◽  
Automated Detection ◽  
Short Period ◽  
Group Velocities

An algorithm for the automatic detection and association of surface waves has been developed and tested over an 18 month interval on broad band data from the Yellowknife array (YKA). The detection algorithm uses a conventional STA/LTA scheme on data that have been narrow band filtered at 20 s periods and a test is then applied to identify dispersion. An average of 9 surface waves are detected daily using this technique. Beamforming is applied to determine the arrival azimuth; at a nonarray station this could be provided by poIarization analysis. The detected surface waves are associated daily with the events located by the short period array at Yellowknife, and later with the events listed in the USGS NEIC Monthly Summaries. Association requires matching both arrival time and azimuth of the Rayleigh waves. Regional calibration of group velocity and azimuth is required. . Large variations in both group velocity and azimuth corrections were found, as an example, signals from events in Fiji Tonga arrive with apparent group velocities of 2.9 3.5 krn/s and azimuths from 5 to + 40 degrees clockwise from true (great circle) azimuth, whereas signals from Kuriles Kamchatka have velocities of 2.4 2.9 km/s and azimuths off by 35 to 0 degrees. After applying the regional corrections, surface waves are considered associated if the arrival time matches to within 0.25 km/s in apparent group velocity and the azimuth is within 30 degrees of the median expected. Over the 18 month period studied, 32% of the automatically detected surface waves were associated with events located by the Yellowknife short period array, and 34% (1591) with NEIC events; there is about 70% overlap between the two sets of events. Had the automatic detections been reported to the USGS, YKA would have ranked second (after LZH) in terms of numbers of associated surface waves for the study period of April 1991 to September 1992.

Surface waves on water of non-uniform depth

1958 ◽  
Vol 4 (6) ◽  
pp. 607-614 ◽  
Author(s):  
Joseph B. Keller
Keyword(s):  
Wave Propagation ◽  
Surface Wave ◽  
Surface Waves ◽  
Linear Theory ◽  
Gravity Waves ◽  
Geometrical Optics ◽  
Surface Wave Propagation ◽  
Special Cases

Gravity waves occur on the surface of a liquid such as water, and the manner in which they propagate depends upon its depth. Although this dependence is described in principle by the equations of the ‘exact linear theory’ of surface waves, these equations have not been solved except in some special cases. Therefore, oceanographers have been unable to use the theory to describe surface wave propagation in water whose depth varies in a general way. Instead they have employed a simplified geometrical optics theory for this purpose (see, for example, Sverdrup & Munk (1944)). It has been used very successfully, and consequently various attempts, only partially successful, have been made to deduce it from the exact linear theory. It is the purpose of this article to present a derivation which appears to be satisfactory and which also yields corrections to the geometrical optics theory.

Surface Wave Propagation in Thin Silver and Aluminium Films

2005 ◽  
Vol 60 (11-12) ◽  
pp. 789-796
Author(s):  
Anouar Njeh ◽  
Nabil Abdelmoula ◽  
Hartmut Fuess ◽  
Mohamed Hédi Ben Ghozlen
Keyword(s):  
Thin Films ◽  
Wave Propagation ◽  
Surface Wave ◽  
Surface Waves ◽  
Acoustic Waves ◽  
Frequency Interval ◽  
Constant Frequency ◽  
Surface Wave Propagation ◽  
Coated Materials ◽  
Bulk Waves

Three kinds of acoustic waves are known: bulk waves, pseudo-surface waves and surface waves. A plane wave section of a constant-frequency surface of a film serves as a hint for the expected nature. Calculations based on slowness curves of films reveal frequency ranges where each type of acoustic waves is predominant. Dispersion curves and displacement acoustic waves are calculated and commented in each frequency interval for different coated materials. Both dispersion and sagittal elliptical displacement are sensitive and depend on diagrams mentioned above. Silver and aluminium thin films having different anisotropy ratios, namely 2.91 and 1.21, are retained for illustration.

The October 6, 1974 Acapulco earthquake: An example of the importance of short-period surface waves in strong ground motion

1978 ◽  
Vol 68 (6) ◽  
pp. 1663-1677
Author(s):  
Stephen H. Hartzell ◽  
James N. Brune ◽  
Jorge Prince
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Epicentral Distance ◽  
Source Region ◽  
Crystalline Rock ◽  
Body Waves ◽  
Wave Number ◽  
Source Depth ◽  
Moment Estimate ◽  
Short Period

abstract The Acapulco earthquake of October 6, 1974 (mb = 5.0, Ms = 4.75) resulted in 0.5 g accelerations in Acapulco at an epicentral distance of about 35 km. Extrapolation of the peak acceleration to the source region gives a near source acceleration of at least 1.0 g. If the teleseismically estimated source depth of 51 km is assumed, the Acapulco accelerogram must be interpreted as composed of primarily body waves. This assumption yields a moment estimate of 3.3 ×1023 dyne-cm and a stress drop of 1.5 kbar. However, strong evidence indicates that the source depth is only about 1.0 km and that the record is composed mainly of high frequency (1.0 to 4.0 Hz) surface waves. The character of the record is that of a normally dispersed surface wave. The relatively simple form and high acceleration may be attributed to the high rigidity, crystalline rock types in the region. The three component record is fitted by summing the fundamental and first higher mode Rayleigh and Love waves using a model consisting of a single layer over a homogeneous half-space. The results are also checked using a direct wave-number integration program developed by Apsel and Luco. The moment estimate from the surface-wave synthetics is 2.0 ×1023 dyne-cm.

The effect of surficial sedimentary layers on continental surface waves

1958 ◽  
Vol 48 (4) ◽  
pp. 339-354 ◽  
Author(s):  
Jack Oliver ◽  
Maurice Ewing
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Frequency Component ◽  
The United States ◽  
High Frequency Component ◽  
Detailed Knowledge ◽  
Mode Propagation ◽  
Long Distance ◽  
Period Range ◽  
Short Period

Abstract Surface waves in the 1/2-second to 12-second period range, recorded at several stations in eastern North America from the eastern Tennessee shock of June 23, 1957, are the bases for several deductions concerning the effect of sedimentary layers on continental surface wave propagation. These are: (1) The velocities of surface waves of the fundamental Love and Rayleigh modes having periods less than about 10 seconds may be strongly affected by sedimentary layers of average thickness. The decrease in velocity accounts, at least in part, for the prolongation of surface-wave trains in this period range when sedimentary layers of appreciable thickness have been traversed. (2) Higher-mode propagation for both types of surface waves is a possible explanation for the velocities, frequencies, and amplitudes of the phase Sg at moderate epicentral distances, and of its long-distance counterpart the high-frequency component of Lg. The lower-frequency components of Lg have been explained previously by other aspects of normal-mode propagation in the crust. (3) Study of dispersion of short-period surface waves can result in fairly detailed knowledge of velocity-depth relation within the sedimentary column and may also reveal information on anisotropy. (4) The results of this study must bear heavily on studies of microseism propagation. As an example, the increase of microseismic activity along the entire east coast of the United States when a storm moves onto the continental shelf may be attributed to channeling of the waves in the deep sedimentary trough beneath the shelf.

Surface-wave dispersion analysis in Mexico City

1995 ◽  
Vol 85 (4) ◽  
pp. 1116-1126
Author(s):  
Francisco J. Chávez-García ◽  
Jaime Ramos-Martínez ◽  
Evangelina Romero-Jiménez
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Ground Motion ◽  
Mexico City ◽  
Rayleigh Waves ◽  
Strong Motion ◽  
Clay Layer ◽  
Period Range ◽  
Wave Trains ◽  
Refraction Data

Abstract In this article, we present an observational investigation of ground motion at Mexico City focused on surface waves. Our purpose is 2-fold; first, to understand incident ground motion during the great Michoacán earthquake of 19 September 1985, and second, to characterize surface waves propagating in the lake-bed zone. To this end we analyze the strong-motion records obtained at Mexico City for the large (MS = 8.1) earthquake of 19 September 1985. It is shown that, in the low-frequency range, we observe the Rayleigh fundamental mode in both the vertical and the radial components, and the Love fundamental mode in the transverse component at all the strong-motion stations. The vertical component also shows the first higher mode of Rayleigh waves. We use a very broadband record obtained at station CU for the smaller (MS = 6.7) earthquake of 14 May 1993 to verify that the dispersion computed from the model of Campillo et al. (1989) represents well the average surface-wave propagation between the coast and Mexico City in the 7- to 10-sec period range. We use this result to assign absolute times to the strong-motion records of the Michoacán event. This allowed us to identify additional wave trains that propagate laterally in directions other than great circle in the 3- to 5-sec period range. These wave trains are identified as Love waves. In a second analysis, we study a set of refraction data obtained during a small-scale (250 m) experiment on the virgin clay of the lake-bed zone. Phase-velocity dispersion curves for several modes of Rayleigh waves are identified in the refraction data and inverted to obtain an S-wave velocity profile. This profile is used as the uppermost layering in a 2D model of Mexico City valley. The results of numerical simulation show that surface waves generated by lateral finiteness of the clay layer suffer large dispersion and attenuation. We conclude that surface waves generated by the lateral heterogeneity of the upper-most stratigraphy very significantly affect ground motion near the edge of the valley, but their importance is negligible for distances larger than 1.5 km from the edge. Thus, locally generated surface waves propagating through the clay layer cannot explain late arrivals observed for the 1985 event. We suggest that the long duration of strong motion is due to the interaction between lateral propagation of waves guided by deep layers (1 to 4 km) and the surficial clay layer. This interaction is possible by the coincidence of the dominant frequency of the uppermost layers and the frequency of the deeply guided waves.

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