Modeling of Ground Deformation and Shallow Surface Waves Generated by Martian Dust Devils and Perspectives for Near-Surface Structure Inversion

2017 ◽  
Vol 211 (1-4) ◽  
pp. 501-524 ◽  
Author(s):  
Balthasar Kenda ◽  
Philippe Lognonné ◽  
Aymeric Spiga ◽  
Taichi Kawamura ◽  
Sharon Kedar ◽  
...  
Keyword(s):  
Surface Waves ◽  
Surface Structure ◽  
Ground Deformation ◽  
Dust Devils ◽  
Near Surface ◽  
Structure Inversion

Joint Inversion Scheme of Dispersive Surface Waves for Near-surface Structure Estimation

2015 ◽  
Author(s):  
Tongju Gong* ◽  
Miao Liu ◽  
Yiming Wang ◽  
Zhiwei Zhu ◽  
Baoqing Zhang
Keyword(s):  
Surface Waves ◽  
Surface Structure ◽  
Joint Inversion ◽  
Near Surface ◽  
Structure Estimation

DISPERSION IN SEISMIC SURFACE WAVES

Geophysics ◽  
1951 ◽  
Vol 16 (1) ◽  
pp. 63-80 ◽  
Author(s):  
Milton B. Dobrin
Keyword(s):  
Surface Waves ◽  
Water Waves ◽  
Seismic Refraction ◽  
Wave Theory ◽  
Wave Dispersion ◽  
Surface Zone ◽  
Surface Wave Dispersion ◽  
Near Surface ◽  
Arrival Times ◽  
Ground Roll

A non‐mathematical summary is presented of the published theories and observations on dispersion, i.e., variation of velocity with frequency, in surface waves from earthquakes and in waterborne waves from shallow‐water explosions. Two further instances are cited in which dispersion theory has been used in analyzing seismic data. In the seismic refraction survey of Bikini Atoll, information on the first 400 feet of sediments below the lagoon bottom could not be obtained from ground wave first arrival times because shot‐detector distances were too great. Dispersion in the water waves, however, gave data on speed variations in the bottom sediments which made possible inferences on the recent geological history of the atoll. Recent systematic observations on ground roll from explosions in shot holes have shown dispersion in the surface waves which is similar in many ways to that observed in Rayleigh waves from distant earthquakes. Classical wave theory attributes Rayleigh wave dispersion to the modification of the waves by a surface layer. In the case of earthquakes, this layer is the earth’s crust. In the case of waves from shot‐holes, it is the low‐speed weathered zone. A comparison of observed ground roll dispersion with theory shows qualitative agreement, but it brings out discrepancies attributable to the fact that neither the theory for liquids nor for conventional solids applies exactly to unconsolidated near‐surface rocks. Additional experimental and theoretical study of this type of surface wave dispersion may provide useful information on the properties of the surface zone and add to our knowledge of the mechanism by which ground roll is generated in seismic shooting.

The Site Tilt and Lander Transfer Function from the Short-Period Seismometer of InSight on Mars

2021 ◽  
Author(s):  
Alexander E. Stott ◽  
Constantinos Charalambous ◽  
Tristram J. Warren ◽  
William T. Pike ◽  
Robert Myhill ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Dust Devils ◽  
Total Change ◽  
Noise Sources ◽  
Element Analysis ◽  
Near Surface ◽  
Seismic Experiment ◽  
Short Period ◽  
Sensitivity Changes

ABSTRACT The National Aeronautics and Space Administration InSight mission has deployed the seismic experiment, SEIS, on the surface of Mars, and has recorded a variety of signals including marsquakes and dust devils. This work presents results on the tilt and local noise sources, which provide context to aid interpretation of the observed signals and allow an examination of the near-surface properties. Our analysis uses data recorded by the short-period sensors on the deck, throughout deployment and in the final configuration. We use thermal decorrelation to provide an estimate of the sol-to-sol tilt. This tilt is examined across deployment and over a Martian year. After each modification to the site, the tilt is seen to stabilize over 3–20 sols depending on the action, and the total change in tilt is <0.035°. Long-term tilt over a Martian year is limited to <0.007°. We also investigate the attenuation of lander-induced vibrations between the lander and SEIS. Robotic arm motions provide a known lander source in the 5–9 Hz bandwidth, yielding an amplitude attenuation of lander signals between 100 and 1000 times. The attenuation of wind sensitivity from the deck to ground presents a similar value in the 1.5–9 Hz range, thus favoring a noise dominated by lander vibrations induced by the wind. Wind sensitivities outside this bandwidth exhibit different sensitivity changes, indicating a change in the coupling. The results are interpreted through a finite-element analysis of the regolith with a depth-dependent Young’s modulus. We argue that discrepancies between this model and the observations are due to local compaction beneath the lander legs and/or anelasticity. An estimate for the effective Young’s modulus is obtained as 62–81 MPa, corroborating previous estimates for the top layer duricrust.

scholarly journals Geophysical imaging of permafrost in the SW Svalbard – the result of two high arctic expeditions to Spitsbergen

2020 ◽  
Author(s):  
Mariusz Majdanski ◽  
Artur Marciniak ◽  
Bartosz Owoc ◽  
Wojciech Dobiński ◽  
Tomasz Wawrzyniak ◽  
...  
Keyword(s):  
Surface Waves ◽  
Active Layer ◽  
High Arctic ◽  
The Arctic ◽  
Seismic Profiles ◽  
Frozen Ground ◽  
Near Surface ◽  
Seismic Processing ◽  
Reflection Seismic ◽  
Sea Coast

<p>The Arctic regions are the place of the fastest observed climate change. One of the indicators of such evolution are changes occurring in the glaciers and the subsurface in the permafrost. The active layer of the permafrost as the shallowest one is well measured by multiple geophysical techniques and in-situ measurements.</p><p>Two high arctic expeditions have been organized to use seismic methods to recognize the shape of the permafrost in two seasons: with the unfrozen ground (October 2017) and frozen ground (April 2018). Two seismic profiles have been designed to visualize the shape of permafrost between the sea coast and the slope of the mountain, and at the front of a retreating glacier. For measurements, a stand-alone seismic stations has been used with accelerated weight drop with in-house modifications and timing system. Seismic profiles were acquired in a time-lapse manner and were supported with GPR and ERT measurements, and continuous temperature monitoring in shallow boreholes.</p><p>Joint interpretation of seismic and auxiliary data using Multichannel analysis of surface waves, First arrival travel-time tomography and Reflection imaging show clear seasonal changes affecting the active layer where P-wave velocities are changing from 3500 to 5200 m/s. This confirms the laboratory measurements showing doubling the seismic velocity of water-filled high-porosity rocks when frozen. The same laboratory study shows significant (>10%) increase of velocity in frozen low porosity rocks, that should be easily visible in seismic.</p><p>In the reflection seismic processing, the most critical part was a detailed front mute to eliminate refracted arrivals spoiling wide-angle near-surface reflections. Those long offset refractions were however used to estimate near-surface velocities further used in reflection processing. In the reflection seismic image, a horizontal reflection was traced at the depth of 120 m at the sea coast deepening to the depth of 300 m near the mountain.</p><p>Additionally, an optimal set of seismic parameters has been established, clearly showing a significantly higher signal to noise ratio in case of frozen ground conditions even with the snow cover. Moreover, logistics in the frozen conditions are much easier and a lack of surface waves recorded in the snow buried geophones makes the seismic processing simpler.</p><p>Acknowledgements               </p><p>This research was funded by the National Science Centre, Poland (NCN) Grant UMO-2015/21/B/ST10/02509.</p>

Tracking of velocity variations at depth in the presence of surface velocity fluctuations

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. U1-U8 ◽  
Author(s):  
Benoit de Cacqueray ◽  
Philippe Roux ◽  
Michel Campillo ◽  
Stefan Catheline
Keyword(s):  
Surface Waves ◽  
Body Waves ◽  
Surface Velocity ◽  
Small Scale ◽  
Beam Forming ◽  
Near Surface ◽  
Velocity Fluctuations ◽  
Wave Separation ◽  
Double Beam ◽  
Velocity Variations

We tested a small-scale experiment that is dedicated to the study of the wave separation algorithm and to the velocity variations monitoring problem itself. It handles the case in which velocity variations at depth are hidden by near-surface velocity fluctuations. Using an acquisition system that combines an array of sources and an array of receivers, coupled with controlled velocity variations, we tested the ability of beam-forming techniques to track velocity variations separately for body waves and surface waves. After wave separation through double beam forming, the arrival time variations of the different waves were measured through the phase difference between the extracted wavelets. Finally, a method was tested to estimate near-surface velocity variations using surface waves or shallow reflection and compute a correction to isolate target velocity variations at depth.

scholarly journals Numerical Evidence of Turbulence Generated by Nonbreaking Surface Waves

2015 ◽  
Vol 45 (1) ◽  
pp. 174-180 ◽  
Author(s):  
Wu-ting Tsai ◽  
Shi-ming Chen ◽  
Guan-hung Lu
Keyword(s):  
Surface Waves ◽  
Water Surface ◽  
Nonlinear Boundary Conditions ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Langmuir Turbulence ◽  
Near Surface ◽  
Order Of Magnitude ◽  
Turbulence Production ◽  
Wave Induced

AbstractNumerical simulation of monochromatic surface waves propagating over a turbulent field is conducted to reveal the mechanism of turbulence production by nonbreaking waves. The numerical model solves the primitive equations subject to the fully nonlinear boundary conditions on the exact water surface. The result predicts growth rates of turbulent kinetic energy consistent with previous measurements and modeling. It also validates the observed horizontal anisotropy of the near-surface turbulence that the spanwise turbulent intensity exceeds the streamwise component. Such a flow structure is found to be attributed to the formation of streamwise vortices near the water surface, which also induces elongated surface streaks. The averaged spacing between the streaks and the depth of the vortical cells approximates that of Langmuir turbulence. The strength of the vortices arising from the wave–turbulence interaction, however, is one order of magnitude less than that of Langmuir cells, which arises from the interaction between the surface waves and the turbulent shear flow. In contrast to Langmuir turbulence, production from the Stokes shear does not dominate the energetics budget in wave-induced turbulence. The dominant production is the advection of turbulence by the velocity straining of waves.

3D elastic full-waveform inversion of surface waves in the presence of irregular topography using an envelope-based misfit function

Geophysics ◽  
2018 ◽  
Vol 83 (1) ◽  
pp. R1-R11 ◽  
Author(s):  
Dmitry Borisov ◽  
Ryan Modrak ◽  
Fuchun Gao ◽  
Jeroen Tromp
Keyword(s):  
Surface Wave ◽  
Objective Function ◽  
Surface Waves ◽  
Large Scale ◽  
Body Wave ◽  
Waveform Inversion ◽  
Full Waveform Inversion ◽  
S Wave ◽  
Near Surface ◽  
Full Waveform

Full-waveform inversion (FWI) is a powerful method for estimating the earth’s material properties. We demonstrate that surface-wave-driven FWI is well-suited to recovering near-surface structures and effective at providing S-wave speed starting models for use in conventional body-wave FWI. Using a synthetic example based on the SEG Advanced Modeling phase II foothills model, we started with an envelope-based objective function to invert for shallow large-scale heterogeneities. Then we used a waveform-difference objective function to obtain a higher-resolution model. To accurately model surface waves in the presence of complex tomography, we used a spectral-element wave-propagation solver. Envelope misfit functions are found to be effective at minimizing cycle-skipping issues in surface-wave inversions, and surface waves themselves are found to be useful for constraining complex near-surface features.

Near-Surface Structure of Plasma Polymer Films Affects Surface Behavior in Water and its Interaction with Proteins

2018 ◽  
Vol 38 (4) ◽  
pp. 851-870 ◽  
Author(s):  
Marianne Vandenbossche ◽  
Gesine Gunkel-Grabole ◽  
Anja Car ◽  
Laetitia Bernard ◽  
Patrick Rupper ◽  
...  
Keyword(s):  
Surface Structure ◽  
Polymer Films ◽  
Plasma Polymer ◽  
Near Surface ◽  
Surface Behavior
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