The High-Resolution Imaging (HRI) Portable Array: A Seismic (and Internet) Network Dedicated to Kilometric-scale Seismic Imaging

Abstract

International audienceWe have developed a network of portable seismic stations dedicated to the high resolution imaging of geological, potentially hazardous, targets. These targets - volcanoes, fault zones, landslide areas - are characterized by strong medium heterogeneities, rugged topography, rough field conditions, and require dedicated equipment in order to maximize the number of recording points. This new network is designed to a) operate experiments with a limited size crew, b) run on low power for possible use in remote areas and difficult conditions, c) record both active and passive seismic sources. The actual network consists of 30 clusters of 9 channels digital acquisition system (DAS), equipped with 6 vertical sensors plus 1 three-component sensor. Each DAS uses Ethernet and 802.11 (WiFi) connections that permit to a single operator to remotely control the entire network. We present the main characteristics of this new portable array, describe the calibration method developed for our sensors and show examples of configuration and recordings for two recent experiments

Joint inversion ofP-wave velocity and density, application to La Soufrière of Guadeloupe hydrothermal system

“…The seismic data were acquired during three successive active surveys that took place between 2001 and 2007. Two different configurations where used: (i) a limited number (10) of standalone seismic stations recorded many small dynamite shots (100-300 g) fired along the 'Chemin des dames' trail around and on top of the dome, (ii) due to the weak signal noise ratio, we then deployed a large number of sensor using the High Resolution Imaging (HRI) facilities (Coutant et al 2008) along different profiles to record few large dynamite shots (1-4 kg) fired in 2 m deep holes. A total of 262 recordings sites and 106 shooting site ( Fig.…”

Muographic mapping of the subsurface density structures in Miura, Boso and Izu peninsulas, Japan

“…Starting with George's 1955 mine gallery experiment 4 , muography has shown that this technique can derive the absolute average density of matter along the muon path and have visualized shallow crustal density distribution inside volcanoes 5 6 7 8 and fault zones 9 10 as well as archaeological objects 11 with better spatial resolution (in the order of a few m) than possible with the conventional techniques, including high resolution seismic tomography 12 13 . Muography can also be utilized to monitor temporal density variations inside large objects, due to, e.g., magma dynamics 14 and underground water table changes 15 , by taking advantage of the almost constant rate of muon flux arriving on Earth.…”

Radiographic visualization of magma dynamics in an erupting volcano

“…A decametric resolution to resolve much finer details requires extremely high recording densities. Recently, Brenguier et al 30 conducted seismic tomography of a conical-shaped volcano with a base diameter of 1 km (approximately the size of Satsuma–Iwojima) and obtained a spatial resolution of 80 m by creating 400 seismic sources (370 sites for 16-ton vibrators and 30 sites for dynamite shots), having received the signals with a High Resolution Imaging Array 31 consisting of 258 seismic sensors. A tomographic measurement of this kind would be both economically and practically out of reach in the harsh field conditions in Satsuma–Iwojima.…”