scholarly journals Humming Trains in Seismology: An Opportune Source for Probing the Shallow Crust

2021 ◽  
Author(s):  
Laura Pinzon-Rincon ◽  
François Lavoué ◽  
Aurélien Mordret ◽  
Pierre Boué ◽  
Florent Brenguier ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Mineral Exploration ◽  
Low Cost ◽  
Complex Structure ◽  
Volcanic Eruptions ◽  
Seismic Source ◽  
Body Waves ◽  
Energy Output ◽  
Passive Seismic ◽  
Shallow Crust

Abstract Seismologists are eagerly seeking new and preferably low-cost ways to map and track changes in the complex structure of the top few kilometers of the crust. By understanding it better, they can build on what is known regarding important, practical issues. These include telling us whether imminent earthquakes and volcanic eruptions are generating telltale underground signs of hazard, about mitigation of induced seismicity such as from deep injection of wastewater, how the Earth and its atmosphere couple, and where accessible natural resources are. Passive seismic imaging usually relies on blind correlations within extended recordings of Earth’s ceaseless “hum” or coda of well-mixed, small vibrations. In this article, we propose a complementary approach. It is seismic interferometry using opportune sources—specifically ones not stationary in time and moving in a well-understood configuration. Its interpretation relies on an accurate understanding of how these sources radiate seismic waves, precise timing, careful placement of pairs of listening stations, and seismic phase differentiation (surface and body waves). Massive freight trains were only recently recognized as such a persistent, powerful cultural (human activity-caused) seismic source. One train passage may generate a tremor with an energy output of a magnitude 1 earthquake and be detectable for up to 100 km from the track. We discuss the source mechanisms of train tremors and review the basic theory on sources. Finally, we present case studies of body- and surface-wave retrieval as an aid to mineral exploration in Canada and to monitoring of a southern California fault zone. We believe noise recovery from this new signal source, together with dense data acquisition technologies such as nodes or distributed acoustic sensing, will deeply transform our ability to monitor activity in the shallow crust at sharpened resolution in time and space.

Humming trains as an opportune source for imaging the shallow crust

2021 ◽  
Author(s):  
Laura Pinzon-Rincon ◽  
François Lavoué ◽  
Aurélien Mordret ◽  
Pierre Boué ◽  
Florent Brenguier ◽  
...  
Keyword(s):  
Mineral Exploration ◽  
Body Waves ◽  
Source Characterization ◽  
Noise Sources ◽  
Estimate Travel Time ◽  
Passive Seismic ◽  
Long Time ◽  
Cultural Noise ◽  
Shallow Crust ◽  
Recovery Approach

<div><span>Freight trains are one of the most powerful and persistent seismic sources of cultural noise. They generate tremors equivalent to earthquakes of magnitude 1 that can be detectable up to 100 km distance.  Here, we propose to use the freight train passages as an opportunistic source of noise for passive seismic interferometry (SI). Usually, passive SI relies on blind correlations of long time series of noise for imaging and monitoring purposes. We suggest an alternative method based on noise source characterization, signal and station pairs selection, and specific seismic phase extraction (surface and body waves) for each virtual source to imaging the subsurface. To illustrate our novel method's potential, we show a case study in Canada's mineral exploration context, where we use retrieved body waves to estimate travel time tomography. This noise recovery approach to create valuable sources could be applied for several seismic noise sources and in different contexts improving spatial and temporal resolutions.</span></div>

Passive Seismic Marchenko Imaging

2020 ◽  
Author(s):  
Zhongyuan Jin
Keyword(s):  
Free Surface ◽  
Seismic Data ◽  
Low Cost ◽  
Body Waves ◽  
Seismic Survey ◽  
Significant Difference ◽  
Passive Seismic ◽  
Seismic Acquisition ◽  
Imaging Property ◽  
Internal Multiples

<p>In recent years, seismic interferometry (SI) has been widely used in passive seismic data, it allows to retrieve new seismic responses among physical receivers by cross-correlation or multidimensional deconvolution (MDD). Retrieval of reflected body waves from passive seismic data has been proved to be feasible. Marchenko method, as a new technique, retrieves Green’s functions directly inside the medium without any physical receiver there. Marchenko method retrieves precise Green’s functions and the up-going and down-going Green’s functions can be used in target-oriented Marchenko imaging, and internal multiples related artifacts in Marchenko image can be suppressed. </p><p>Conventional Marchenko imaging uses active seismic data, in this abstract, we propose the method of passive seismic Marchenko imaging (PSMI) which retrieves Green’s functions from ambient noise signal. PSMI employs MDD method to obtain the reflection response without free-surface interaction as an input for Marchenko algorithm, such that free-surface multiples in the retrieved shot gathers can be eliminated, besides, internal multiples don’t contribute to final Marchenko image, which means both free-surface multiples and internal multiples have been taken into account. Although the retrieved shot gathers are contaminated by noises, the up-going and down-going Green’s functions can be still retrieved. Results of numerical tests validate PSMI’s feasibility and robustness. PSMI provides a new way to image the subsurface structure, it combines the low-cost property of passive seismic acquisition and target-oriented imaging property of Marchenko imaging, as well as the advantage that there are no artifacts caused by internal multiples and free-surface multiples.</p><p>Overall, the significant difference between PSMI and conventional Marchenko imaging is that passive seismic data is used into Marchenko scheme, which extends the Marchenko imaging to passive seismic field. Passive seismic Marchenko imaging avoids the effects of free-surface multiples and internal multiples in the retrieved shot gathers. PSMI combines the low-cost property of passive seismic acquisition and target-oriented imaging property of Marchenko imaging which is promising in future field seismic survey.</p><p>This work is supported by the Fundamental Research Funds for the Central Universities (JKY201901-03). </p>

Seismic solutions utilizing existing in-mine infrastructure for mineral exploration: A case study from Maseve platinum mine, South Africa

2022 ◽  
Vol 41 (1) ◽  
pp. 54-61
Author(s):  
Moyagabo K. Rapetsoa ◽  
Musa S. D. Manzi ◽  
Mpofana Sihoyiya ◽  
Michael Westgate ◽  
Phumlani Kubeka ◽  
...  
Keyword(s):  
South Africa ◽  
Seismic Data ◽  
Mineral Exploration ◽  
Ground Surface ◽  
Seismic Survey ◽  
Noisy Environment ◽  
Borehole Data ◽  
Passive Seismic ◽  
Below Ground

We demonstrate the application of seismic methods using in-mine infrastructure such as exploration tunnels to image platinum deposits and geologic structures using different acquisition configurations. In 2020, seismic experiments were conducted underground at the Maseve platinum mine in the Bushveld Complex of South Africa. These seismic experiments were part of the Advanced Orebody Knowledge project titled “Developing technologies that will be used to obtain information ahead of the mine face.” In these experiments, we recorded active and passive seismic data using surface nodal arrays and an in-mine seismic land streamer. We focus on analyzing only the in-mine active seismic portion of the survey. The tunnel seismic survey consisted of seven 2D profiles in exploration tunnels, located approximately 550 m below ground surface and a few meters above known platinum deposits. A careful data-processing approach was adopted to enhance high-quality reflections and suppress infrastructure-generated noise. Despite challenges presented by the in-mine noisy environment, we successfully imaged the platinum deposits with the aid of borehole data and geologic models. The results open opportunities to adapt surface-based geophysical instruments to address challenging in-mine environments for mineral exploration.

An experimental study of source motion synthesis from first arrivals

1963 ◽  
Vol 53 (5) ◽  
pp. 955-963
Author(s):  
Henry N. Pollack
Keyword(s):  
Experimental Study ◽  
Source Function ◽  
Seismic Source ◽  
The Body ◽  
Body Waves ◽  
Fixed Position ◽  
Explosive Source ◽  
Simple Medium ◽  
Surface Ice ◽  
Source Motion

Abstract The motion near a seismic source is synthesized from experimentally obtained seismograms of non-dispersed body waves. The body waves were emitted from an explosive source submerged in a lake with a frozen surface. The seismograms were recorded at several distances by moving the source to a greater depth for each record, while the seismometer remained in a fixed position on the surface ice sheet. All syntheses of the waveform one meter from the source yield the impulsive nature of the source. Deviations between the synthesized one-meter record and the observed one-meter motion are thought to reflect primarily the changing character of the shot medium with depth from the ice. These results indicate that over the short propagation distances (about three wavelengths for the higher frequencies recorded) through the simple medium of this experiment, the observed waveforms and their associated spectra retain characteristics of the source function. The records also yield some information regarding the nature and structure of the elastic medium about the source.

scholarly journals Increment in the volcanic unrest and number of eruptions after the 2012 large earthquakes sequence in Central America

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gino González ◽  
Eisuke Fujita ◽  
Bunichiro Shibazaki ◽  
Takumi Hayashida ◽  
Giovanni Chiodini ◽  
...  
Keyword(s):  
Central America ◽  
Seismic Waves ◽  
Dynamic Stress ◽  
Reaction Times ◽  
Volcanic Eruptions ◽  
Large Magnitude ◽  
Tectonic Earthquakes ◽  
The Impact ◽  
The Relationship ◽  
Large Earthquakes

AbstractUnderstanding the relationship cause/effect between tectonic earthquakes and volcanic eruptions is a striking topic in Earth Sciences. Volcanoes erupt with variable reaction times as a consequence of the impact of seismic waves (i.e. dynamic stress) and changes in the stress field (i.e. static stress). In 2012, three large (Mw ≥ 7.3) subduction earthquakes struck Central America within a period of 10 weeks; subsequently, some volcanoes in the region erupted a few days after, while others took months or even years to erupt. Here, we show that these three earthquakes contributed to the increase in the number of volcanic eruptions during the 7 years that followed these seismic events. We found that only those volcanoes that were already in a critical state of unrest eventually erupted, which indicates that the earthquakes only prompted the eruptions. Therefore, we recommend the permanent monitoring of active volcanoes to reveal which are more susceptible to culminate into eruption in the aftermath of the next large-magnitude earthquake hits a region.

scholarly journals Seismic anisotropy: an original tool to understand the geodynamic evolution of the Italian peninsula

1997 ◽  
Vol 40 (3) ◽  
Author(s):  
L. Margheriti ◽  
C. Nostro ◽  
A. Amato ◽  
M. Cocco
Keyword(s):  
Upper Mantle ◽  
Common Property ◽  
Seismic Waves ◽  
Seismic Anisotropy ◽  
Structural Features ◽  
Relative Strength ◽  
Plate Motion ◽  
Mantle Minerals ◽  
Anisotropic Bodies ◽  
Shallow Crust

Anisotropy is a common property of the Earth's crust and the upper mantle; it is related to the strain field of the medium and therefore to geodynamics. In this paper we describe the different possible origins of anisotropic behavior of the seismic waves and the seismological techniques used to define anisotropic bodies. In general it is found that the fast polarization direction is parallel to the absolute plate motion in cratonic areas, to the spreading direction near rifts or extensional zones, and to the main structural features in transpressive regimes. The delay times between fast and slow waves reflect the relative strength and penetration at depth of the deformation field. The correspondence between surface structural trends and anisotropy in the upper mantle, found in many regions of the world, strongly suggest that orogenic processes involve not only the shallow crust but the entire lithosphere. Recently in Italy both shear wave splitting analysis and Pn inversion were applied to define the trend of seismic anisotropy. Along the Northern Appeninic arc fast directions follow the strike of the arc (i.e., parallel to the strike of the Miocene-Pleistocene compressional features), whereas in the Tyrrhenian zone fast directions are about E-W SW-NE; parallel to the post-Miocene extension that is thought to have reoriented the mantle minerals fabric in the astenosphere.

scholarly journals On the point-source approximation of earthquake dynamics

2014 ◽  
Vol 57 (3) ◽  
Author(s):  
Andrea Bizzarri
Keyword(s):  
Point Source ◽  
Seismic Waves ◽  
Single Point ◽  
Seismic Source ◽  
Transition Process ◽  
Point Sources ◽  
Multiple Point ◽  
Earthquake Dynamics ◽  
Planar Fault ◽  
Source Models

<p>The focus on the present study is on the point-source approximation of a seismic source. First, we compare the synthetic motions on the free surface resulting from different analytical evolutions of the seismic source (the Gabor signal (G), the Bouchon ramp (B), the Cotton and Campillo ramp (CC), the Yoffe function (Y) and the Liu and Archuleta function (LA)). Our numerical experiments indicate that the CC and the Y functions produce synthetics with larger oscillations and correspondingly they have a higher frequency content. Moreover, the CC and the Y functions tend to produce higher peaks in the ground velocity (roughly of a factor of two). We have also found that the falloff at high frequencies is quite different: it roughly follows ω<span><sup>−2</sup></span> in the case of G and LA functions, it decays more faster than ω<span><sup>−2</sup></span> for the B function, while it is slow than ω<span><sup>−1</sup></span> for both the CC and the Y solutions. Then we perform a comparison of seismic waves resulting from 3-D extended ruptures (both supershear and subshear) obeying to different governing laws against those from a single point-source having the same features. It is shown that the point-source models tend to overestimate the ground motions and that they completely miss the Mach fronts emerging from the supershear transition process. When we compare the extended fault solutions against a multiple point-sources model the agreement becomes more significant, although relevant discrepancies still persist. Our results confirm that, and more importantly quantify how, the point-source approximation is unable to adequately describe the radiation emitted during a real world earthquake, even in the most idealized case of planar fault with homogeneous properties and embedded in a homogeneous, perfectly elastic medium.</p>

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.

Improved Piezoelectric Performance of Electrospun PVDF Nanofibers with Conductive Paint Coated Electrode

2019 ◽  
Vol 19 (02) ◽  
pp. 1950008 ◽  
Author(s):  
R. Tamil Selvan ◽  
W. A. D. M. Jayathilaka ◽  
A. Hilaal ◽  
S. Ramakrishna
Keyword(s):  
Contact Area ◽  
Electrode Material ◽  
Polyvinylidene Fluoride ◽  
Electrode Materials ◽  
Low Cost ◽  
Short Circuit ◽  
Open Circuit ◽  
Energy Output ◽  
Piezoelectric Performance ◽  
Conductive Paint

Fabrication of Nanogenerators (NGs) using Electrospun polyvinylidene fluoride (PVDF) nanofibers for sensing and energy harvesting applications is a trending research due to its flexibility, biocompatibility, low-cost, etc. Different electrode materials, polymer composites had been proposed to increase the energy output. However, the contact area between the electrode material and nanofiber mat which helps to conduct more piezoelectric charges to the electrode surface are still unexplored especially at nanoscale level. In this paper, authors have proposed the use of low-cost carbon conductive paint to increase the contact area between the electrode and nanofiber mat. The electrode material is coated with conductive paint and the NG was fabricated with that electrode to compare the performances with conventional NG. Piezoelectric performance of the proposed NG has increased substantially as it generates an open circuit voltage [Formula: see text]) of 4.5[Formula: see text]V and short circuit current [Formula: see text]) of 25[Formula: see text]nA, whereas the conventional NG can only produce 1.6 [Formula: see text]) and 1.5[Formula: see text]nA [Formula: see text]). A drop test experiment was conducted, and the device consistency was verified experimentally.

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