H
Y
Last name: HELLO
First name: Yann
International audience
Dans des zones de subduction, 80/100 de l'énergie sismique est libérée en mer, parfois à proximité de côtes très peuplées comme sur le pourtour de l'océan Pacifique. D'où l'intérêt de mesurer précisément l'activité sismique dans ces zones vulnérables.
We have developed autonomous, Lagrangian floats that make seismo-acoustic measurements in the oceans, with mission durations of 4+ years and running (http://earthscopeoceans.org). Earthquakes generate seismic waves that traverse the solid earth, convert to acoustic waves when they hit the seafloor from below, and are recorded by the hydrophone...
Lagrangian floats are used since the early 2000s for monitoring temperature and salinity of the oceans, and more recently for recording tele-seismic waves. This technology is originally dedicated to global monitoring because it's drifting with oceanic currents over thousands of kilometers. Recent developments have shown that the floats can also...
International audience
A fruitful close collaboration between teams of researchers and engineers of Geoazur, a research laboratory specializing in seismic observation, and Osean, a dynamic company combining the talents of engineers in low-noise, low-power electronics specialized in underwater acoustics, gives this instrument a guarantee of robustness, reliability and...
Autonomous floats have been used for decades to monitor physical properties of the oceans. More recently, these instruments have been used to record seismic signals in the oceans in order to improve tomographic images resolution at the global scale. A hydrophone is used to monitor the acoustic landscape but all the data cannot be sent through...
Monitoring of the oceans with autonomous floats is of great interest for many disciplines. Monitoring on a global scale needs a multidisciplinary approach to be affordable. For this purpose, we propose an approach that allows oceanographers from different specialities to develop applications for autonomous floats. However, developing such...
Mermaid stands for Mobile Earthquake Recording in Marine Areas by Independent Divers. This autonomous, freely-drifting underwater robot records acoustic conversions of earthquake signals while floating at a water depth of 1.5 km, rising to the surface to transmit such seismograms by satellite. Mermaid is already in use for seismic tomography,...
We propose a new method to study the response of a hydrophone at very low frequencies. In our method, the hydrophone is placed in a calibration chamber filled with water and, by instantaneously changing the water height, an abrupt pressure increase of about 1000 Pa is produced. The pressure variation mathematically corresponds to an input...
At 2000 m depth in the oceans, one can hear biological, seismological, meteorological, and anthropogenic activity. Acoustic monitoring of the oceans at a global scale and over long periods of time could bring important information for various sciences. The Argo project monitors the physical properties of the oceans with autonomous floats, some...
International audience
Long-term monitoring of the ocean, for instance its seismic activity, remains a technical and a financial challenge. Despite technological advances in reducing the size and consumption of electronic components, in providing powerful energy through Lithium batteries, and in reducing the size of sensors, the new generation of stand-alone...
Using earthquakes and seismic noise recordings on a broad-band station installed in October 2016 on the slope of the Nice airport at 17 m depth, we find a strong site amplification of the seismic waves (factor 10 around a frequency of 1Hz).The effects of superficial layers on the amplitude, frequency and duration of seismic waves (often called...
The European Space Agency's Aeolus satellite mission is designed to provide global information on the wind speed from the ground up to 30 km, which is highly demanded for weather forecasting. Aeolus satellite has been set into orbit in August 2018 and its payload consists of a sophisticated ALADIN lidar instrument measuring wind velocity by...
Our understanding of the internal dynamics of the Earth is largely based on images of seismic velocity variations in the mantle obtained with global tomography. However, our ability to image the mantle is severely hampered by a lack of seismic data collected in marine areas. Here we report observations made under different noise conditions (in...
A smart city must be equipped with efficient and interconnected transportation. Unfortunately, economic or operational reasons for creating an infrastructure sometimes compete with imperatives of natural hazards. The case of Nice Cote d'Azur airport is an interesting example. As air traffic increased, the airport has been progressively...
We propose a new probabilistic scheme for the automatic recognition of underwater acoustic signals generated by teleseismic P-waves recorded by hydrophones in the ocean. The recognition of a given signal is based on the relative distribution of its power among different frequency bands. The signal's power distribution is compared with a...
Two thirds of the surface of our planet are covered by water and are still poorly instrumented, which has prevented the earth science community from addressing numerous key scientific questions. The potential to leverage the existing fiber optic seafloor telecom cables that criss-cross the oceans, by turning them into dense arrays of...
The abyssal velocity of the Northern Current, in the north-western Mediterranean has been estimated using for the first time MERMAIDs, i.e. submarine drifting instruments that record seismic waves. In this study the Northern Current shows an intense activity even in deep layers of the water column. Through pseudo-eulerian statistics different...
A broadband seismological station (PRIMA) installed offshore Nice airport (southeastern France) reveals a strong amplification effect of seismic waves. PRIMA station was in operation for 2 years (9/2016 to 10/2018) on the outer shelf at a water depth of 18 m. Situated at the mouth of the Var River, this zone is unstable and prone to landslides....