The role of Interferometric Synthetic Aperture Radar in Detecting, Mapping, Monitoring, and Modelling the Volcanic Activity of Piton de la Fournaise, La Réunion: A Review

Synthetic Aperture Radar (SAR) remote sensing plays a significant role in volcano monitoring despite the measurements’ non real-time nature. The technique’s capability of imaging the spatial extent of ground motion has especially helped to shed light on the location, shape, and dynamics of subsurface magmatic storage and transport as well as the overall state of activity of volcanoes worldwide. A variety of different deformation phenomena are observed at exceptionally active and frequently erupting volcanoes, like Piton de la Fournaise on La Réunion Island. Those offer a powerful means of investigating related geophysical source processes and offer new insights into an active volcano’s edifice architecture, stability, and eruptive behavior. Since 1998, Interferometric Synthetic Aperture Radar (InSAR) has been playing an increasingly important role in developing our present understanding of the Piton de la Fournaise volcanic system. We here collect the most significant scientific results, identify limitations, and summarize the lessons learned from exploring the rich Piton de la Fournaise SAR data archive over the past ~20 years. For instance, the technique has delivered first evidence of the previously long suspected mobility of the volcano’s unsupported eastern flank, and it is especially useful for detecting displacements related to eruptions that occur far away from the central cone, where Global Navigation Satellite System (GNSS) stations are sparse. However, superimposed deformation processes, dense vegetation along the volcano’s lower eastern flank, and turbulent atmospheric phase contributions make Piton de la Fournaise a challenging target for applying InSAR. Multitemporal InSAR approaches that have the potential to overcome some of these limitations suffer from frequent eruptions that cause the replacement of scatterers. With increasing data acquisition rates, multisensor complementarity, and advanced processing techniques that resourcefully handle large data repositories, InSAR is progressively evolving into a near-real-time, complementary, operational volcano monitoring tool. We therefore emphasize the importance of InSAR at highly active and well-monitored volcanoes such as Mount Etna, Italy, Kīlauea Volcano, Hawai’i, and Piton de la Fournaise, La Réunion.

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Ground Based Interferometric Synthetic Aperture Radar Combined With a Critical Slope Monitoring Program Will Provide Early Detection of Slope Movement Along Pipeline Corridors

ASME-ARPEL 2019 International Pipeline Geotechnical Conference ◽

10.1115/ipg2019-5333 ◽

2019 ◽

Author(s):

Steven E. Borron ◽

Martin P. Derby

Keyword(s):

Synthetic Aperture Radar ◽

Real Time ◽

Visual Presentation ◽

Slope Movement ◽

Synthetic Aperture ◽

Interferometric Synthetic Aperture Radar ◽

Atmospheric Conditions ◽

Technical Requirements ◽

Radar Systems ◽

Aperture Radar

Abstract The transition of satellite InSAR technology to a ground-based system provides a proven risk reduction technology if combined with a critical slope monitoring (CSM) program. Together the technology with the active engagement of a defined program can detect the onset of slope displacement, acceleration, and provide a method to determine slope collapse. Recently, using the radar software, Guardian, and its ability to document surface velocity in intervals of 24-hours or less has allowed for the development of site-specific levels of rockfall risk. The ground-based InSAR (interferometric synthetic aperture radar) systems and their near real-time capabilities allow for proactive and early warning monitoring. The technical requirements include the ability to operate 24/7 in all weather conditions, acquire data in near real-time, and visually present data in an interpretable format that requires no end user processing. Since slope failure without acceleration is unlikely, the rapid visual presentation of processed data becomes a crucial component for a CSM technology. The definition of the CSM program not only requires short intervals for data acquisition, processing, and visual presentation but also requires a monitoring professional that can interpret and communicate changes in slope movement. A specific CSM technology requirement demands, acquiring data at a continuous interval of 2-minutes or less, 24 hours per day for the duration of the monitoring project. Also, the CSM technology must be able to transmit alarm messages at the moment thresholds are met, visually present data with various time series plots, including displacement, and velocity maps while acquired radar data is continuously updated and with no end-user processing. A site-specific document called a trigger action response plan (TARP) needs to be prepared at the start of any CSM project. Currently, only the IBIS-FM and ArcSAR radars developed by IDS (Ingegneria Dei Sistemi) GeoRadar can meet the technical requirements of the defined CSM technology. During a CSM program, the short interval between each data acquisition provides two specific advantages. First, the short acquisition interval decreases interpolation, which automatically increases data confidence. Second, the short intervals also decrease the effects of atmospheric changes that are a part of all data acquisitions. Although the IBIS-FM and ArcSAR radar systems can operate in nearly all-weather conditions, sudden changes in local atmospheric conditions can still exhibit data effects. Both radar systems include active proprietary algorithms that account for ongoing atmospheric changes during acquisitions. In comparison, some remote sensing data acquired from, LIDAR, and total station technologies can be critically affected by sudden changes in local atmospheric conditions. Combining the near real-time capabilities of an interferometric synthetic aperture radar system with a dedicated professional will decrease risk to people and property by allowing slope movement trends to be identified and observed in near real-time, 24-hours per/day. The paper will discuss the highlights of several successful CSM programs. We describe deployment versatility, the ability to identify the onset of displacement accurately, and the critical identification of the onset of acceleration.

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