ISTerre - Institut des Sciences de la Terre

GDB2 : Managing our mineral resources for a sustainable future : The role of earth scientists.

Marian RAMIREZ NINO — 2020-05-05T13:30:02Z

Séminaire de l'équipe Ondes et structures

– Date

8 May 2020 - 14h00 at EGU2020 : Sharing Geoscience Online

– Webinar Description :

The UN widely promotes the Sustainable Development Goals, 17 common goals to a sustainable future for our planet and its citizens. By 2030 Europe aims to reduce greenhouse gas emissions by at least 40% (compared with 1990). The accelerating exploitation of our ecosystems has been highlighted annually by Earth Overshoot Days. The urgent need to combat climate change requires that we significantly increase use of clean energies and energy storage and decrease our non-energy emissions. But the infrastructure needed for the transition to a low-carbon society will require the production and consumption of vast amounts of mineral products, not only the much publicised critical metals but also more common mineral products like copper, iron and sand.

The circular economy has been lauded as a solution to the increased demand on resources and related climate impacts. Reducing waste and improving efficiencies are essential. However, given (i) increasing populations and improving living standards globally, (ii) the decades-long duration that many raw materials are in use, (iii) the difficulties and/or environmental impact of recovering and recycling some materials, and (iv) the strain on our energy, land and water resources, it is time to define the role of the geoscience community in managing Earth resources and achieving a more sustainable future.

We will also need to provide our expertise to the wider public conversations about our natural resources : Is it reasonable the public think the circular economy can be applied to all items we consume ? Where will substitutions come from ? One of our responsibilities must be to communicate effectively with politicians, industry and the general public to strengthen the science message.

The webinar is organized by the PACIFIC H2020 project [1] and presented as one of EGU's Great Debates of the Geosciences

Speakers :
– Dr. Karen Hanghøj : Director of British Geological Survey
– Dr. Saleem Ali : University of Delaware
– Dr. Andy Whitmore : Co-chair, London Mining Network
– Dr. Patrick Redmond : Kobold Metals

Chair : Dr Aoife Braiden, Geological Survey Ireland

Webinar Registration
https://us02web.zoom.us/webinar/register/WN_cwOCquTpScmwBge8nJIlxw

[1] PACIFIC has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 776622.

Retrieving the reflection events from passive seismic using Radon correlation

Marian RAMIREZ NINO — 2020-03-02T13:55:09Z

Séminaire de l'équipe Ondes et structures

par Diako H. Naghadeh - Dublin Institute for Advanced Studies

– Date

06 mars 2020 à 11h30

– Lieu

Salle Dolomieu, ISTerre Grenoble

Since explosive and impulsive sources such as dynamites, air guns, gas guns, even Vibroseis can have a big impact on the environment, many companies decided to record ambient noises and use it to estimate the physical properties of the subsurface. A big challenge appears when the target is extracting body waves from recorded passive signals especially in regions with the severe low-velocity weathered layer. Those waves are usually weak and surface waves are prominent in passive signals. To understand the characteristics of passive signals and the effect of natural source locations a simple two-layer synthetic model was created. A staggered finite difference method has used to solve the elasto-dynamic equations to simulate the propagation of elastic waves in that model. To extract body waves from simulated passive signals we propose and test Radon correlation that helps suppress surface waves based on the propagation velocity and amount of move out. Radon correlation is a time-spatial correlation of amplitudes on a train of Dirac delta functions through different hyperbolic paths. It is tested on synthetic 2D model data prior to its application to real recorded passive data. Synthetic tests are representing a clear body wave extraction due to applied the introduced method that cannot be seen in a general correlation result. It is possible to generate virtual shot gathers by applying Radon Correlation into a linear array of receivers and make relevant velocity model by the general processing module.

The high potential of Distributed acoustic sensing on seafloor optical cable for seismology, ocean solid-earth interactions and maritime traffic monitoring.

Marian RAMIREZ NINO — 2020-02-12T09:34:21Z

Séminaire de l'équipe Ondes et structures

par Diane Rivet - Geoazur, OCA, UCA , CNRS

– Date

14 février 2020 à 11h00

– Lieu

Salle Dolomieu, ISTerre Grenoble

Measuring seismic and acoustic signals on seafloor telecom cables has proven recently its very high potential for earthquake monitoring but also for better other applications.

Distributed acoustic sensing over oceanic telecom cables offer the unique ability to measure in a very dense manner the ocean solid-earth interaction and microseism that are generated on the seafloor. At shallow depth (<100m), close to the coast (<10km), we measure the pressure changes caused by the oceanic gravity waves. The bottom pressure is then compared to a meteorological buoy located a few kilometers away from the cable. The amplitude and frequency of the pressure are modulated by the gravity waves height and periods. DAS observations of gravity waves (amplitude – frequency – azimuth) over 6km provide a more detail description of the wave field than a single buoy.

A consequence of gravity wave interactions is the local generation of microseismic noise on both coastal regions and in the deep ocean. Theses noises that propagate across continents are central to a large fraction of todays' seismic imagery and monitoring campaigns. At depth larger than a 1km, we observe Scholte waves at the ocean-solid earth interface produced by the non-linear interaction of gravity waves. The amplitude and frequency are also modulated similarly to the gravity waves observed close to the coast. Besides, the frequency-wave number decomposition of the signal reveals that a larger fraction of the noise is generated close to the coast. These observations confirm that these deep Scholte waves are secondary microseismic noise, generated from the interaction of landward gravity waves with oceanward gravity wave reflected on the coast.

Finally we measure the noise emitted by a tanker cruising one day at a distance of 5.8 km from the shore, above 85m of water, and the following day at a distance of 20 km from the shore, above 2000 m of water. These results confirm the high potential of DAS technology using telecom cable for a remote and quantitative monitoring of the maritime trafic and for vessel tracking on shallow water but also at great depth.

Multicomponent Rayleigh-wave crosscorrelation waveform inversion for ambient seismic sources

Marian RAMIREZ NINO — 2019-11-13T09:39:23Z

Séminaire de l'équipe Ondes et structures

par Zongbo Xu, Ph.D. candidate from Boise State University

– Date

15 Novembre 2019 à 11h00

– Lieu

Salle Dolomieu, ISTerre Grenoble

Abstract :

Ambient seismic source information is important for subsurface investigations and source studies. Crosscorrelation-based seismic interferometry is commonly used to retrieve surface-wave Green's functions from ambient seismic noise recordings. This approach requires that seismic sources are isotropically distributed in all directions around two receivers. However, this assumption is rarely valid in practice. If one combines the source information (like locations and strengths) with the seismic interferometry, one can still accurately estimate structure information. The distributions of some ambient seismic sources (e.g. microseisms) change with time and thus attract lots of research interests. We present an approach to estimate spatially distributed ambient seismic sources by inversion of seismic wavefield noise crosscorrelations. We demonstrate the benefits of using multicomponent crosscorrelations in this source estimation process. We present a shallow near-surface case study and a preliminary estimation of the Antarctic primary microseism in February 2010.

Anisotropic three components energy partition in coda wave observed by S-net

Marian RAMIREZ NINO — 2019-09-30T13:44:26Z

Séminaire de l'équipe Ondes et structures

par Kaoru SAWAZAKI, NIED - Japan

– Date

1 octobre 2019 à 14h00

– Lieu

l'Amphithéâtre KILIAN , ISTerre Grenoble

Extracting surface waves from ambient seismic noise recorded by S-net for imaging shallow subduction zone along the Japan trench

Marian RAMIREZ NINO — 2019-09-30T13:44:01Z

Séminaire de l'équipe Ondes et structures

par Ryota Takagi - Tohoku University, Japan

– Date

1 octobre 2019 à 15h00

– Lieu

l'amphithéâtre KILIAN, ISTerre Grenoble

Machine Learning Reveals the Seismic Signature of Eruptive Behavior at Piton de la Fournaise Volcano

Marian RAMIREZ NINO — 2019-09-02T08:40:42Z

Séminaire de l'équipe Ondes et structures

par Chris Ren - Los Alamos National Laboratory, United States

– Date

13 Septembre 2019 à 11h00

– Lieu

Salle Dolomieu, ISTerre Grenoble