International Initiatives

The Geohazard Supersites and Natural Laboratories initiative began with the "Frascati declaration" at the conclusion of the 3rd International Geohazards workshop of GEO held in November 2007 in Frascati, Italy. The recommendation of the workshop was "to stimulate an international and intergovernmental effort to monitor and study selected reference sites by establishing open access to relevant datasets according to GEO principles, to foster the collaboration between all various partners and end-users". This recommendation was later formalized in the GEO Work Plan as Component 2 of the GEO task DI-01, part of the GEO Disasters Societal Benefit Area.

Today GSNL has grown to a voluntary collaboration among monitoring agencies, scientific community and the CEOS space agencies, working to improve the scientific understanding of earthquake and volcanic phenomena and enable better risk assessment and emergency management.

According to its principles, actions in GSNL are focused on specific areas of the world, the Supersites, for which large amounts of in situ and satellite data are made openly available to all scientists. These areas are selected based on the importance of the scientific problems, as well as on the amount of population at risk, and should be evenly distributed among developed and less developed countries.

Seven Supersites have been established to date, six of which on volcanic areas (Hawaii, US; Icelandic volcanoes; Mt. Etna, IT; Campi Flegrei, IT; Ecuadorian volcanoes, Taupo, NZ), and one on a seismic area (Western North Anatolian fault, TR). Two more proposals are being evaluated: the San Andreas Fault, and the La Reunion volcano.

The Supersites have succeeded  in promoting new scientific developments by various research groups, however the level of success in providing actual societal benefits cannot be easily ascertained.

For some Supersites there is a close coordination between scientists and end-users, who are in fact part of the teams, but in some other cases the end-users are not involved, and the uptake of the new science is not optimised and can be lengthy and/or incomplete.

The new vision for the GSNL initiative (GSNL 2.0) promotes more coordinated scientific efforts and stronger ties with the end-user community, to ensure more immediate and direct benefits in Disaster Risk Management.

The status of the GSNL initiative, the opportunities for involvement, and the future development for the GSNL 2.0 will be presented at the workshop and discussed with the scientific community.

ARIA is a joint JPL/Caltech project to automate synthetic aperture radar (SAR) and GPS imaging capabilities for scientific understanding, hazard response, and societal benefit. We have built a quasi-operational SAR and GPS data system that forms the foundation for hazard monitoring and response capability, as well as providing imaging capabilities important for science studies.  Together, InSAR and GPS have the ability to capture surface deformation in high spatial and temporal resolution. For earthquakes, this deformation provides information that is complementary to seismic data on location, geometry and magnitude of earthquakes.  Accurate location information is critical for understanding the regions affected by damaging shaking.  Regular surface deformation measurements from SAR and GPS are useful for monitoring changes related to many processes that are important for hazard and resource management such as volcanic deformation, groundwater withdrawal, and landsliding.  

Observations of SAR coherence change have a demonstrated use for damage assessment for hazards such as earthquakes, tsunamis, hurricanes, and volcanic eruptions.  These damage assessment maps can be made from imagery taken day or night and are not affected by clouds, making them valuable complements to optical imagery.  The coherence change caused by the damage from hazards (building collapse, flooding, ash fall) is also detectable with intelligent algorithms, allowing for rapid generation of damage assessment maps over large areas at fine resolution, down to the spatial scale of single family homes.

We present progress and results we have made on automating analysis of SAR data for hazard monitoring and response using data from the international constellation of InSAR satellites including the Italian Space Agency’s (ASI) COSMO-SkyMed constellation of X-band SAR satellites and the Canadian Space Agency's Radarsat II C-band satellite.   Since the beginning of our project, we have imaged deformation and coherence change caused by many natural hazard events around the world with the resulting products being used both by the science community and response groups needing improved situational awareness.  This project is enabled by a collaboration between JPL/Caltech/CIDOT and NASA/ASI.

This work has to be intended to be submitted to GSNL initiative

The well-documented historical earthquakes and the ones occurred in the last century in the Marmara Region indicate that the segments of the North Anatolian Fault Zone (NAFZ) are seismically active and have the capability of generating destructive earthquakes. Earthquake records spanning two millennia reveal that, on average, at least one medium intensity (Io=VII-VIII) event has affected Istanbul every 50 years. For this reason, the FP7 MARsite project (New Directions in Seismic Hazard assessment through Focused Earth Observation in Marmara Supersite), supported by EU, is aimed at providing the most complete geodetic records of crustal deformation for any major continental earthquake occurring in the Marmara region through repeat GPS, InSAR, gravity and seismological observations.

In the framework of this project, we intend to perform a long-term continuous geodetic monitoring of the crustal deformation affecting the Istanbul area by benefiting from large archives of X-band satellite SAR data, made available through the Supersites Initiatives. To this aim, we processed the available SAR datasets by exploiting the advanced multi-temporal and multi-scale InSAR techniques, known as the Small BAseline Subset (SBAS) approach (Berardino et al., 2002) and the StaMPS Persistent Scatterer Interferometry (PSI) method (Hooper et al., 2007), which have the potential of providing new insights into the spatial and temporal pattern of the investigated phenomena.

In this work, the results achieved in the first 2 years of the MARsite project by IREA-CNR and INGV groups via the exploitation of X-band SAR datasets over the megacity of Istanbul are presented. In particular, IREA-CNR applied the SBAS technique to a dataset of 101 SAR images acquired by the TerraSAR-X constellation over descending orbits. From this SAR dataset, which spans the time interval from November 2010 to August 2014, 312 differential interferograms were generated with a spatial separation (perpendicular baseline) between the acquisition orbits of less than 500 m. The most important feature we observe is a generalized stability over the study area, except for some localized displacements, related to subsidence and slope instability phenomena. In particular, we identified a displacement pattern related to the Istanbul airport, showing a mostly linear deformation trend with a velocity of about 1 cm/yr, although a slowdown effect is observed starting from early 2014. Moreover, we observed another deforming area in the area of the Miniaturk park with a higher velocity of about 1.5 cm/yr.

INGV applied the StaMPS PSI approach (Hooper et al., 2007) to COSMO-SkyMed SAR images acquired from two different ascending tracks, consisting of 29 and 64 image strips for the Eastern and the Western tracks respectively, and covering the period between 2011 and 2013. Two sets of 28 and 63 differential interferograms were generated for the two tracks. The first results on the Eastern track show that the presence of mountains and vegetation strongly limit the number of coherent pixels in non-urban areas, anyway the time series in general show an approximately linear trend, other than where very local effects occur. Concerning the Western track, the mean ground velocities vary between -2 and 1 cm/yr; the time series are noisier than those for the Eastern track, but show in general a linear trend with small non linear components. There is no evident trend at long spatial wavelengths, while many locally deforming areas are present.

These preliminary InSAR results represent a key point in the context of long-term deformation analyses, which are crucial for seismic hazard assessment. Indeed, they provide space-time information on the ground displacements that can be exploited to better understand/model/interpret the physical processes behind the observed deformation phenomena at different temporal and spatial scales.

References

Berardino, P., Fornaro, G., Lanari, R., Sansosti, E., 2002, A new Algorithm for Surface Deformation Monitoring based on Small Baseline Differential SAR Interferograms, IEEE Trans. Geo. Rem. Sens., 40, 11, 2375-2383.

Hooper, A., Segall, P., Zebker H., 2007, Persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis, with application to Volcan Alcedo, Galapagos, J. Geophys. Res., 112, B07407.

THEME: Supersites, hazard mitigation, risk reduction       

 KEY WORDS: InSAR, SBAS, optical data, modeling

Based on the official definition of Supersites available at “supersites.earthobservations.org/phase2.php”, two Supersites proposals on Vesuvius-Campi Flegreii and Etna active volcanic areas (Southern Italy), have been submitted and recently approved by CEOS, with the Istituto Nazionale di Geofisica e Vulcanologia (Italy), namely the “Osservatorio Vesuviano” Naples branch and the “Osservatorio Etneo” Catania branch, as the reference scientific institution.

In this regard, according to the CEOS acceptance letters for both areas, a considerable amount of satellite data has been granted by Space Agencies, with InSAR (X, C and L-band data, archive + future acquisitions) and optical data.

Data processing for the Italian Supersites volcanoes already started in the framework of the MED-SUV (“MEDiterranean SUpersites Volcanoes”) FP-7 EU-funded project, which will financially support the Supersites activities until May, 2016, in a “collaborative area”, involving 24 national and international project partners from highly qualified research institutions and small and medium enterprises.

In this regard, deformation signals affecting the investigated areas have been obtained by processing a large archive of SAR data acquired at X-band from 2009 to 2014 by the COSMO-SkyMed sensors through the well-known InSAR algorithm referred to as Small Baseline Subset (SBAS) approach [1]. Information coming from X-band time-series has been also complemented with historical displacement time-series obtained at C-band by analyzing the available ENVISAT archives spanning the time period from 2002 to 2010. Also, a few ALOS-PALSAR data have been used to fully characterize the deformation over the two Supersites. For notable unrest episodes single interferograms have also been produced and analyzed by exploiting a TerraSAR-X set of images. Finally, on Etna volcano, the activities have been focused on the improvement and standardization of integrated DInSAR interferometry approaches, adequate when a limited number of SAR scenes are available. In the project’s framework the exploitation of optical data has been also significant, making it possible the generation of products that may be used to support volcanic risk monitoring, offering a prompt response for hazard mitigation. Noteworthy, optical EO data (AVHRR, MODIS) are directly broadcasted from various satellites at different times of the day through owned INGV multi-mission antennas and real-time processed at INGV laboratory in Rome.

Collected satellite-based displacement signals (single deformation as well as DInSAR time-series), coupled with in-situ geodetic data, represent the starting point for subsequent analyses aimed at inverting the geodetic data (terrestrial and space one simultaneously) in order to retrieve the sources responsible for the measured deformation signals.

In this regard, the nonlinear inversion method of Camacho et al. [2] has been employed for modeling pressure or/and mass sources with a free geometry, not a proscribed shape such as a sphere or ellipse. The method assumes simple homogenous elastic conditions, and models the size and location of pressure/mass sources in a general model, fitting the entire geodetic data set within some regularity conditions. The approach [2, 3] works as a growth process that constructs a very general geometrical configuration and a general framework for the geometry of anomalous bodies is achieved by partitioning the subsurface volume into a dense 3-D grid of point sources.

Results of these activities will be hereby presented and discussed.   

REFERENCES

[1] Berardino, P., Fornaro, G., Lanari, R., Sansosti, E., 2002, A new Algorithm for Surface Deformation Monitoring based on Small Baseline Differential SAR Interferograms, IEEE Trans. Geo. Rem. Sens., 40, 11, 2375-2383.

[2] Camacho, A. G., P. J. González, J. Fernández, and G. Berrino (2011), Simultaneous inversion of surface deformation and gravity changes by means of extended bodies with a free geometry: Application to deforming calderas, J. Geophys. Res., 116, B10401, doi:10.1029/2010JB008165.

[3] Samsonov, S. V., K. F. Tiampo, A. G. Camacho, J. Fernández, and P. J. González, 2014. Spatiotemporal analysis and interpretation of 1993–2013 ground deformation at Campi Flegrei, Italy, observed by advanced DInSAR. Geophys. Res. Lett., 41, 6101-6108, doi: 10.1002/2014GL060595.

UNAVCO is a non-profit, university-governed consortium that operates the National Science Foundation’s Geodesy Advancing Geosciences and EarthScope (GAGE) facility and hosts the Western North America InSAR Consortium (WInSAR). The NASA-supported seamless synthetic aperture radar archive (SSARA) project at UNAVCO has implemented a distributed access system for SAR data and derived data products (i.e. interferograms) through the use of simple web services.  The development efforts of the SSARA project increase the accessibility and the utility of SAR science data to solid Earth and cryospheric science researchers. Specifically, SSARA provides simple web services tools to more seamlessly and effectively exchange and share SAR metadata, archived data and on-demand derived products between the distributed archives, individual users, and key information technology development systems such as the NASA/JPL ARIA projects or ESA’s Supersites Exploitation Platform that provide higher level resources for geodetic data processing, data assimilation and modeling, and integrative analysis for scientific research and hazards applications.  One component of SSARA is the federated query service that provides users a single search interface for SAR metadata housed at the Alaska Satellite Facility and UNAVCO (WInSAR and EarthScope data archives) through a unified application programming interface (API).  SSARA also provides digital elevation model (DEM) access for topographic correction via a simple web service through OpenTopography and tropospheric correction products through JPL’s OSCAR service.  Interest from the international community has prompted an effort to incorporate other SAR data archives (the ESA Virtual Archive 4 and the DLR TerraSAR-X_SSC Geohazard Supersites and Natural Laboratories collections) into the SSARA federated query service to expand access to data for researchers outside the US and North America.  Under the SSARA project, a user-contributed InSAR archive for interferograms, time series, and other derived data products has been developed at UNAVCO. The InSAR archive is based on a standard data format and provides storage, distribution, and sharing of research results within the geodesy community. The tools and services developed for SSARA help overcome current obstacles including heterogeneous archive access protocols and data product formats, data provider access policy constraints, and an increasingly broad and diverse selection of SAR data to address the need to efficiently discover, access, retrieve, distribute, and process large quantities of new and diverse data.

WInSAR is a consortium of non-commercial scientists at 144
institutions engaged in radar remote sensing research and education,
with major emphasis on InSAR studies in the western part of North
America. WInSAR is hosted by UNAVCO, Inc. and both organizations are
non-profit, membership-governed groups funded by the National
Aeronautics and Space Administration (NASA), the U.S. Geological
Survey and the National Science Foundation (NSF). To help maximize the
scientific return of InSAR data, WInSAR provides password-protected
data access with partners including the Geohazard Supersite and
Natural Laboratories initiative of the Group on Earth Observations
(GEO), the Alaska Satellite Facility, and the various space
agencies. Data access follows the regulations from the space agency
that created the data, and so there are different amounts of data
available to different approved investigators and depending on the
country of origin of the WInSAR member.  All members have access to
the Caltech/JPL/Stanford open source software called ISCE (InSAR
Scientific Computing Environment), and even non-members can attend the
short courses hosted by UNAVCO.  We present here a summary of recent
results by WInSAR scientists that are based largely or in part on
Sentinel, ERS, and Envisat SAR data analysis, with additional SAR data
from other satellites and the NASA airborne InSAR system called
UAVSAR. Studies have addressed deformation related to the earthquake
cycle, volcanoes, glaciers, landslides, subsidence due to groundwater
withdrawal and subsurface energy production (including hydrocarbons
and geothermal), and wetland dynamics in a number of locations. These
studies include assessment, forecasting, and response to geohzards as
well as fundamental research about Earth processes.

The recent unrest and activity within the Bárðarbunga volcanic system, Iceland was initially identified by the onset of an intense earthquake swarm on the 16^th August 2014. Over the following weeks interferograms formed using X-band satellite images from COSMO-SkyMed (CSK) and TerraSAR-X (TSX) satellites were analysed in near real-time and used to map ground displacements associated with the initial dyke emplacement and propagation (NE of Bárðarbunga), responsible for the sudden unrest. On the 29^th August 2014, a small fissure opened up just a few kilometers to the north of the Vatnajökull ice cap, at Holuhraun. The eruption lasted only a few hours, but was followed on 31^st August by the onset of a fissure eruption, characterised by lava fountaining and the extrusion of extensive lava flows. The eruption continues at the time of writing (November 2014).

We demonstrate how Interferometric Synthetic Aperture Radar (InSAR) analysis, in conjunction with earthquake seismicity and GPS measurements, has been instrumental in the continued monitoring of Bárðarbunga volcanic system since the onset of unrest. We also investigate how changes in the local stress field induced by the dyke intrusion and concurrent magma withdrawal may trigger seismicity and potentially renewed activity at neighbouring volcanoes.

As part of the Center on Earth Observation Satellites (CEOS) Icelandic Supersite Initiative, the Italian Space Agency (ASI) re-tasked CSK satellites in July 2014 at the request of staff at the University of Iceland, to commence acquiring both ascending and descending images every 16 days over Bárðarbunga volcano and also over Askja volcano, extending south to the tip of the Vatnajökull ice cap. TSX images were also being acquired in the vicinity of Askja volcano and the northern edge of the Vatnajökull glacier and delivered under the German Aerospace Center (DLR) Icelandic Supersite User Agreement. As the unrest/eruption progressed, CSK SAR images were acquired more frequently in the vicinity of both the eruption site at Holuhraun and Bárðarbunga volcano. In some cases scenes were acquired with repeat intervals of just 24 hours, enabling the formation of one day interferograms which maintained coherence on the surface of the ice cap and exhibited phenomenal deformation at the site of the sub-glacial Bárðarbunga caldera.

InSAR analysis has systematically been used throughout the eruption to track the emplacement of the lava flows, estimate their surface area and monitor co-eruptive displacement in the vicinity of both the dyke and the eruption site, along with major co-eruptive subsidence occurring beneath the Bárðarbunga caldera – the latter is believed to have commenced shortly after the onset of the unrest and is associated with magma withdrawal beneath the central volcano, feeding the dyke and the ongoing eruption.

The vast amount of new SAR data, provided through the Icelandic SUPERSITE, has driven a strategy of rapid SAR processing and analysis of ground deformation during the 2014 Bárðarbunga unrest and eruption. This has significantly facilitated an improved understanding of the sub-surface plumbing beneath one of Iceland’s most active volcanoes.