scholarly journals Seismic Velocity Response to Atmospheric Pressure Using Time-Lapse Passive Seismic Interferometry

2021 ◽  
Author(s):  
Chloé Gradon ◽  
Florent Brenguier ◽  
Johannes Stammeijer ◽  
Aurélien Mordret ◽  
Kees Hindriks ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Seismic Velocity ◽  
Barometric Pressure ◽  
Specific Response ◽  
Positive Trend ◽  
Seismic Velocities ◽  
Near Surface ◽  
Passive Seismic ◽  
Velocity Changes ◽  
Shallow Crust

ABSTRACT Seismic velocities in the shallow crust down to a few kilometers depth show a remarkable sensitivity to stress perturbations due to the presence of compliant pores, cracks, fractures, and faults. Monitoring temporal changes of seismic velocities can thus provide key insights on dynamic processes affecting the shallow crust such as those related to the atmosphere (rainfall, barometric pressure, and temperature) and those with deeper tectonic and volcanic origins. In this work, we investigate the specific response of the near surface down to 300 m depth to atmospheric pressure variations. We conduct a four month passive seismic monitoring experiment in the desert of Oman using continuous noise recorded at geophones located within five wells. The results show a clear, direct correlation between seismic velocities and barometric pressure variations for monthly transients. At a longer, seasonal temporal scale, seismic velocities are stable, whereas atmospheric pressure shows a clear positive trend. We use the undrained coupled poroelastic theory to model these observations and find that the lack of seasonal velocity changes can be partly explained by the atmospheric pressure that diffuses into the pores with a strong hydraulic diffusivity likely higher than 100  m2/s consistent with the local geology referring to carbonates. Finally, the comparison between the modeled and observed velocity changes leads to estimate a velocity–stress sensitivity on the order of 6.3×10−7  Pa−1 which is consistent with previous studies. Using this result for calibration, we find that a sudden step-change drop of velocity of 0.015% occurring in the beginning of October 2019 and corresponding to a stress perturbation likely larger than 240 Pa affected the entire studied area. This small change could be related to a perturbation at greater depth associated with variations in the production rates within the underlying reservoir.

scholarly journals Physics-Based Relationship for Pore Pressure and Vertical Stress Monitoring Using Seismic Velocity Variations

2021 ◽  
Vol 13 (14) ◽  
pp. 2684
Author(s):  
Eldert Fokker ◽  
Elmer Ruigrok ◽  
Rhys Hawkins ◽  
Jeannot Trampert
Keyword(s):  
Pore Pressure ◽  
Seismic Velocity ◽  
Pressure Head ◽  
Groundwater Table ◽  
Surface Velocity ◽  
Seismic Velocities ◽  
Stress Monitoring ◽  
Near Surface ◽  
Velocity Variations ◽  
Velocity Changes

Previous studies examining the relationship between the groundwater table and seismic velocities have been guided by empirical relationships only. Here, we develop a physics-based model relating fluctuations in groundwater table and pore pressure with seismic velocity variations through changes in effective stress. This model justifies the use of seismic velocity variations for monitoring of the pore pressure. Using a subset of the Groningen seismic network, near-surface velocity changes are estimated over a four-year period, using passive image interferometry. The same velocity changes are predicted by applying the newly derived theory to pressure-head recordings. It is demonstrated that the theory provides a close match of the observed seismic velocity changes.

scholarly journals Toward Using Seismic Interferometry to Quantify Landscape Mechanical Variations after Earthquakes

2021 ◽  
Author(s):  
Odin Marc ◽  
Christoph Sens-Schönfelder ◽  
Luc Illien ◽  
Patrick Meunier ◽  
Manuel Hobiger ◽  
...  
Keyword(s):  
Landslide Susceptibility ◽  
Seismic Velocity ◽  
Landslide Hazard ◽  
Seismic Velocities ◽  
Surface Strength ◽  
Near Surface ◽  
Single Station ◽  
Seismic Velocity Changes ◽  
Velocity Changes ◽  
Large Earthquakes

ABSTRACT In mountainous terrain, large earthquakes often cause widespread coseismic landsliding as well as hydrological and hydrogeological disturbances. A subsequent transient phase with high landslide rates has also been reported for several earthquakes. Separately, subsurface seismic velocities are frequently observed to drop coseismically and subsequently recover. Consistent with various laboratory work, we hypothesize that the seismic-velocity changes track coseismic damage and progressive recovery of landscape substrate, which modulate landslide hazard and hydrogeological processes, on timescales of months to years. To test this, we analyze the near-surface seismic-velocity variations, obtained with single-station high-frequency (0.5–4 Hz) passive image interferometry, in the epicentral zones of four shallow earthquakes, for which constraints on landslide susceptibility through time exist. In the case of the 1999 Chi-Chi earthquake, detailed landslide mapping allows us to accurately constrain an exponential recovery of landslide susceptibility with a relaxation timescale of about 1 yr, similar to the pattern of recovery of seismic velocities. The 2004 Niigata, 2008 Iwate, and 2015 Gorkha earthquakes have less-resolved constraints on landsliding, but, assuming an exponential recovery, we also find matching relaxation timescales, from ∼0.1 to ∼0.6  yr, for the landslide and seismic recoveries. These observations support our hypothesis and suggest that systematic monitoring of seismic velocities after large earthquakes may help constrain and manage the evolution of landslide hazard in epicentral areas. To achieve this goal, we end by discussing several ways to improve the link between seismic velocity and landscape mechanical properties, specifically by better constraining time-dependent near-surface strength and hydrogeological changes. Hillslopes displaying coseismic surface fissuring and displacement may be an important target for future geotechnical analysis and coupled to passive geophysical investigations.

scholarly journals Noise-based ballistic wave passive seismic monitoring. Part 1: body waves

2020 ◽  
Vol 221 (1) ◽  
pp. 683-691 ◽  
Author(s):  
F Brenguier ◽  
R Courbis ◽  
A Mordret ◽  
X Campman ◽  
P Boué ◽  
...  
Keyword(s):  
Seismic Velocity ◽  
Noise Source ◽  
Seismic Monitoring ◽  
Body Waves ◽  
P Wave ◽  
New Technique ◽  
Apparent Velocity ◽  
Near Surface ◽  
Velocity Increase ◽  
Passive Seismic

SUMMARY Unveiling the mechanisms of earthquake and volcanic eruption preparation requires improving our ability to monitor the rock mass response to transient stress perturbations at depth. The standard passive monitoring seismic interferometry technique based on coda waves is robust but recovering accurate and properly localized P- and S-wave velocity temporal anomalies at depth is intrinsically limited by the complexity of scattered, diffracted waves. In order to mitigate this limitation, we propose a complementary, novel, passive seismic monitoring approach based on detecting weak temporal changes of velocities of ballistic waves recovered from seismic noise correlations. This new technique requires dense arrays of seismic sensors in order to circumvent the bias linked to the intrinsic high sensitivity of ballistic waves recovered from noise correlations to changes in the noise source properties. In this work we use a dense network of 417 seismometers in the Groningen area of the Netherlands, one of Europe's largest gas fields. Over the course of 1 month our results show a 1.5 per cent apparent velocity increase of the P wave refracted at the basement of the 700-m-thick sedimentary cover. We interpret this unexpected high value of velocity increase for the refracted wave as being induced by a loading effect associated with rainfall activity and possibly canal drainage at surface. We also observe a 0.25 per cent velocity decrease for the direct P-wave travelling in the near-surface sediments and conclude that it might be partially biased by changes in time in the noise source properties even though it appears to be consistent with complementary results based on ballistic surface waves presented in a companion paper and interpreted as a pore pressure diffusion effect following a strong rainfall episode. The perspective of applying this new technique to detect continuous localized variations of seismic velocity perturbations at a few kilometres depth paves the way for improved in situ earthquake, volcano and producing reservoir monitoring.

scholarly journals Characterization of a complex near-surface structure using well logging and passive seismic measurements

2016 ◽  
Author(s):  
Beatriz Benjumea ◽  
Albert Macau ◽  
Anna Gabàs ◽  
Sara Figueras
Keyword(s):  
Wave Velocity ◽  
Upper Cretaceous ◽  
Seismic Velocity ◽  
Well Logging ◽  
P Wave ◽  
Geophysical Field ◽  
Near Surface ◽  
Passive Seismic ◽  
Surface Geology ◽  
Seismic Measurements

Abstract. We combine geophysical well logging and passive seismic measurements to characterize the near surface geology of an area located in Hontomin, Burgos (Spain). This area has some near-surface challenges for a geophysical study. The irregular topography is characterized by limestone outcrops and unconsolidated sediments areas. Additionally, the near surface geology includes an upper layer of pure limestones overlying marly limestones and marls (Upper Cretaceous). These materials lie on top of Low Cretaceous siliciclastic sediments (sandstones, clays, gravels). In any case, decreasing seismic velocity with depth is expected. The geophysical datasets used in this study include sonic and gamma ray logs at two boreholes and passive seismic measurements: 224 H/V stations and 3 arrays. Well logging data defines two significant changes in the P-wave velocity log within the Upper Cretaceous layer and one more at the Upper to Lower Cretaceous contact. This technique has also used for refining the geological interpretation. The passive seismic measurements provide a map of sediment thickness with maximum of around 40 m and shear-wave velocity profiles from the array technique. A comparison between seismic velocity coming from well logging and array measurements defines the resolution limits of the passive seismic techniques and helps for its interpretation. This study shows how these low-cost techniques can provide useful information about near-surface complexity that could be used for designing a geophysical field survey or for seismic processing steps such as statics or imaging.

Passive seismic velocity monitoring of natural faults: The FaultScan project

2020 ◽  
Author(s):  
Florent Brenguier ◽  
Aurelien Mordret ◽  
Yehuda Ben-Zion ◽  
Frank Vernon ◽  
Pierre Boué ◽  
...  
Keyword(s):  
Seismic Velocity ◽  
Fault Zones ◽  
Body Waves ◽  
Fault System ◽  
Seismic Arrays ◽  
San Jacinto Fault ◽  
Highway Network ◽  
Seismic Velocity Changes ◽  
Passive Seismic ◽  
Velocity Changes

<p>Laboratory experiments report that detectable seismic velocity changes should occur in the vicinity of fault zones prior to earthquakes. However, operating permanent active seismic sources to monitor natural faults at seismogenic depth has been nearly impossible to achieve. The FaultScan project (Univ. Grenoble Alpes, Univ. Cal. San Diego, Univ. South. Cal.) aims at leveraging permanent cultural sources of ambient seismic noise to continuously probe fault zones at a few kilometers depth with seismic interferometry. Results of an exploratory seismic experiment in Southern California demonstrate that correlations of train-generated seismic signals allow daily reconstruction of direct P body-waves probing the San Jacinto Fault down to 4 km depth. In order to study long-term earthquake preparation processes we will monitor the San Jacinto Fault using such approach for at least two years by deploying dense seismic arrays in the San Jacinto Fault region. The outcome of this project may facilitate monitoring the entire San Andreas Fault system using the railway and highway network of California. We acknowledge support from the European Research Council under grant No.~817803, FAULTSCAN.</p>

SEISMIC VELOCITIES IN THE SOUTHEASTERN SAN JOAQUIN VALLEY OF CALIFORNIA

Geophysics ◽  
1941 ◽  
Vol 6 (4) ◽  
pp. 327-355
Author(s):  
E. J. Stulken
Keyword(s):  
Seismic Data ◽  
Seismic Velocity ◽  
San Joaquin Valley ◽  
Seismic Velocities ◽  
Velocity Measurements ◽  
Constant Depth ◽  
Entire Area ◽  
Velocity Gradients ◽  
Velocity Changes ◽  
First Time

For the first time, seismic velocity measurements from well surveys have been made intensively enough to justify an analysis of the velocity field in an entire area instead of just along lines between wells. Maps are drawn showing velocity changes in the southeastern San Joaquin Valley of California. A portion of the valley floor in the neighborhood of Bakersfield, about twenty‐five miles wide and thirty‐five miles long, was chosen for study because of the number of wells in the area whose velocities were known. Differences in average velocity of 1700 feet per second for a constant depth are observed, and horizontal velocity gradients averaging over 100 feet per second per mile are computed. Correction schemes for the adjustment of seismic data are suggested, and correction maps shown. An attempt is made to establish a connection between stratigraphy and seismic velocity. Comparative study of the logs of wells and the velocities observed in them yields certain qualitative conclusions, but attempts to express the relation in a quantitative way fail.

scholarly journals Estimation of water content in a temperate glacier from radar and seismic sounding data

2003 ◽  
Vol 37 ◽  
pp. 317-324 ◽  
Author(s):  
Beatriz Benjumea ◽  
Yury Ya. Macheret ◽  
Francisco J. Navarro ◽  
Teresa Teixidό
Keyword(s):  
Radio Wave ◽  
Water Content ◽  
Electromagnetic Waves ◽  
Seismic Velocity ◽  
Ice Cores ◽  
Radar Data ◽  
Seismic Velocities ◽  
Near Surface ◽  
Seismic Sounding ◽  
Water Contents

AbstractRadio-wave velocity measurements in temperate and polythermal glaciers, combined with dielectric mixture formulae by Looyenga or Paren, have been used during the last decade to estimate the water content in temperate ice. We have used a similar mixture formula by Riznichenko, but based on elastic properties of the material, to estimate the water content from seismic velocity data. To compare the suitability of the two methods, we have used seismic and radar data from a temperate glacier on an Antarctic island. The estimated water contents are within 0.4–2.3% (average 1.2 ±0.6%) when radio-wave velocities are used, and within 0.9–3.2% (average 2.2±0.9%) when seismic velocities are used. These results are similar to those directly measured from ice cores and to those estimated from radar data on other temperate glaciers. The water-content estimates from seismic data are higher than those from radar data, which we attribute to the different behaviour of seismic and radar velocities as functions of density. Near-surface conditions (ice–firn conditions, presence of crevasses, etc.) have a strong influence on the propagation of elastic and electromagnetic waves, and thus on the accuracy of the velocity determinations and water-content estimates, and so should not be disregarded.

scholarly journals A P-wave velocity model of the upper crust of the Sannio region (Southern Apennines, Italy)

1998 ◽  
Vol 41 (4) ◽  
Author(s):  
G. Iannaccone ◽  
L. Improta ◽  
P. Capuano ◽  
A. Zollo ◽  
G. Biella ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Seismic Velocity ◽  
Carbonate Platform ◽  
Velocity Model ◽  
P Wave ◽  
Seismic Velocities ◽  
Upper Crust ◽  
Near Surface ◽  
P Wave Velocity ◽  
Apulia Platform

This paper describes the results of a seismic refraction profile conducted in October 1992 in the Sannio region, Southern Italy, to obtain a detailed P-wave velocity model of the upper crust. The profile, 75 km long, extended parallel to the Apenninic chain in a region frequently damaged in historical time by strong earthquakes. Six shots were fired at five sites and recorded by a number of seismic stations ranging from 41 to 71 with a spacing of 1-2 km along the recording line. We used a two-dimensional raytracing technique to model travel times and amplitudes of first and second arrivals. The obtained P-wave velocity model has a shallow structure with strong lateral variations in the southern portion of the profile. Near surface sediments of the Tertiary age are characterized by seismic velocities in the 3.0-4.1 km/s range. In the northern part of the profile these deposits overlie a layer with a velocity of 4.8 km/s that has been interpreted as a Mesozoic sedimentary succession. A high velocity body, corresponding to the limestones of the Western Carbonate Platform with a velocity of 6 km/s, characterizes the southernmost part of the profile at shallow depths. At a depth of about 4 km the model becomes laterally homogeneous showing a continuous layer with a thickness in the 3-4 km range and a velocity of 6 km/s corresponding to the Meso-Cenozoic limestone succession of the Apulia Carbonate Platform. This platform appears to be layered, as indicated by an increase in seismic velocity from 6 to 6.7 km/s at depths in the 6-8 km range, that has been interpreted as a lithological transition from limestones to Triassic dolomites and anhydrites of the Burano formation. A lower P-wave velocity of about 5.0-5.5 km/s is hypothesized at the bottom of the Apulia Platform at depths ranging from 10 km down to 12.5 km; these low velocities could be related to Permo-Triassic siliciclastic deposits of the Verrucano sequence drilled at the bottom of the Apulia Platform in the Apulia Foreland.

Near-salt stress-induced seismic velocity changes and seismic anisotropy and their impacts on salt imaging: A case study in the Kuqa depression, Tarim Basin, China

2020 ◽  
Vol 8 (3) ◽  
pp. T487-T499
Author(s):  
Yunqiang Sun ◽  
Gang Luo ◽  
Yaxing Li ◽  
Mingwen Wang ◽  
Xiaofeng Jia ◽  
...  
Keyword(s):  
Salt Stress ◽  
Seismic Anisotropy ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Seismic Velocities ◽  
Kuqa Depression ◽  
Velocity Models ◽  
Salt Structure ◽  
Seismic Velocity Changes ◽  
Velocity Changes

It has been recognized that stress perturbations in sediments induced by salt bodies can cause elastic-wave velocity (seismic velocity) changes and seismic anisotropy through changing their elastic parameters, thus leading to difficulties in salt imaging. To investigate seismic velocity changes and seismic anisotropy by near-salt stress perturbations and their impacts on salt imaging, taking the Kuqa depression as an example, we have applied a 2D plane-strain static geomechanical finite-element model to simulate stress perturbations and calculate the associated seismic velocity changes and seismic anisotropy; then we used the reverse time migration and imaging method to image the salt structure by excluding and including the stress-induced seismic velocity changes. Our model results indicate that near-salt stresses are largely perturbed due to salt stress relaxation, and the stress perturbations lead to significant changes of the seismic velocities and seismic anisotropy near the salt structure: The maximum seismic velocity changes can reach approximately 20% and the maximum seismic anisotropy can reach approximately 10%. The significant changes of seismic velocities due to stress perturbations largely impact salt imaging: The salt imaging is unclear, distorted, or even failed if we exclude near-salt seismic velocity changes from the preliminary velocity structure, but the salt can be better imaged if the preliminary velocity structure is modified by near-salt seismic velocity changes. We find that the locations where salt imaging tends to fail usually occur where large seismic velocity changes happen, and these locations are clearly related to the geometric characteristics of salt bodies. To accurately image the salt, people need to integrate results of geomechanical models and stress-induced seismic velocity changes into the imaging approach. The results provide petroleum geologists with scientific insights into the link between near-salt stress perturbations and their induced seismic velocity changes and help exploration geophysicists build better seismic velocity models in salt basins and image salt accurately.

scholarly journals Crustal seismic velocity responds to a magmatic intrusion and seasonal loading in Iceland’s Northern Volcanic Zone

2019 ◽  
Vol 5 (11) ◽  
pp. eaax6642 ◽  
Author(s):  
C. Donaldson ◽  
T. Winder ◽  
C. Caudron ◽  
R. S. White
Keyword(s):  
Atmospheric Pressure ◽  
Seismic Velocity ◽  
Volumetric Strain ◽  
Volcanic Zone ◽  
Noise Interferometry ◽  
Crustal Stresses ◽  
Single Station ◽  
Seismic Velocity Changes ◽  
Velocity Changes ◽  
Snow Thickness

Seismic noise interferometry is an exciting technique for studying volcanoes, providing a continuous measurement of seismic velocity changes (dv/v), which are sensitive to magmatic processes that affect the surrounding crust. However, understanding the exact mechanisms causing changes in dv/v is often difficult. We present dv/v measurements over 10 years in central Iceland, measured using single-station cross-component correlation functions from 51 instruments across a range of frequency bands. We observe a linear correlation between changes in dv/v and volumetric strain at stations in regions of both compression and dilatation associated with the 2014 Bárðarbunga-Holuhraun dike intrusion. Furthermore, a clear seasonal cycle in dv/v is modeled as resulting from elastic and poroelastic responses to changing snow thickness, atmospheric pressure, and groundwater level. This study comprehensively explains variations in dv/v arising from diverse crustal stresses and highlights the importance of deformation modeling when interpreting dv/v, with implications for volcano and environmental monitoring worldwide.

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