The Seismic Hazards activity set its objectives based on priorities elaborated through consultation with users and practitioners of satellite EO and geohazards. Specialists of satellite Earth Observation (EO) and risk assessment defined their objectives and EO data requirements through an open review process in the framework of the 2012 International Forum on Satellite Earth Observations (the Santorini report) and Geohazards.
In 2014, a Seismic Hazards Pilot activity was launched intending to last for 3 years and aiming to:
- Support the generation of globally self-consistent strain rate estimates and the mapping of active faults at the global scale by providing interferometric synthetic aperture radar (InSAR) and optical data and processing capacities to existing initiatives (wide extent satellite observations)
- Continue to support the Geohazard Supersites and Natural Laboratories initiative (GSNL) for the seismic hazard activities (satellite observations focused on supersites)
- Develop and demonstrate advanced science products for rapid earthquake response (observation of earthquakes with low to intermediate magnitude, M>5.8)
The Pilot has successfully addressed the challenges of the seismic hazards community.
In particular, during the Seismic Hazards Pilot, a variety of terrain motion mapping products have been generated and published to better understand the nature of the earthquakes, either in the context of the Geohazard Supersites (Event Supersites) or as part of the pilot’s Objective C). The following seismic events have been investigated using EO data to map the ground deformation and model the seismic source parameters: Greece (Cephalonia) in January-February 2014, Nepal (Gorkha) in April 2015 (see The Nepal Event Supersite below), Greece (Lefkada) in November 2015, Ecuador (Muisne) in April 2016, Italy (Amatrice, Visso, Norcia) in August-October 2016 and New Zealand (Kaikoura) in November 2016. In the cases of the Ecuador (see The 2016 Ecuador earthquake below) and Italy earthquakes in 2016, the value-added products were provided to civil protection authorities in order to understand the extent of the affected areas and better focus their activities during the emergency.
Furthermore, InSAR measurements have been validated against GNSS measurements and GPS velocities over California (US) and part of the North Anatolian Fault (Turkey). Concerning active faults, the Pilot started mapping the Sagaing fault (Myanmar) and the San Ramon fault (Chile) using tri-stereo Pleiades imagery. These activities shall be completed in the frame of a follow-on Demonstrator activity that is about to start within 2018.
Finally, the Pilot in collaboration with the Geohazards Exploitation Platform (GEP) managed to showcase the growing need for online capabilities to support data access, processing tools and services and an e-collaboration environment to share seismic products.
Some successful examples of the Pilot activity are described below in detail.
The Nepal Event Supersite
The area of Nepal deeply affected by the M7.9 earthquake of April 25, 2015, became an Event Supersite soon after the mainshock, following requests from the geophysical scientific community to the Geohazard Supersite and Natural Laboratory initiative of GEO (www.earthobservations.org/gsnl_es_nepal.php).
Many CEOS agencies started to acquire satellite data over the Supersite, and ESA, ASI, CSA, DLR, NASA, USGS provided access at no-cost to GSNL users for these data. JAXA provided ALOS-2 data for the earthquake through the Seismic Hazards pilot Objective C. Data from ground networks were provided by UNAVCO and IRIS.
A number of scientific products were generated –among others– by INGV, NASA JPL, COMET, CNR-IREA and IPGP to measure the displacement and were combined with geological data to map the precise shape of the fault plane at depth and the amount of relative slip of the fault limbs.
The Event Supersite page provided reference to the data resources and also, for the first time, to several scientific products freely shared in digital form to allow re-use by scientists.
The data and the products were also provided to:
- end-users such as decision-making bodies e.g. National Disaster Management Authority (NDMA) and National Emergency Operation Centre (NEOC)
- local scientific institutions in charge such as the National Society for Earthquake Technology (NSET) and other academic institutions
- the international scientific community, through scientific papers or web-stories.
Figure 1. ALOS-2 deformation map generated by JPL NASA shows uplift and southward motion of central Nepal, including Kathmandu.
“While the ESA Sentinel-1 satellite provided very important results, the role of commercial radar missions was also crucial to better resolve the details of the ground deformation and the seismic source. A substantial step forward towards exploiting the full societal benefit of satellite data would arise from the automatic provision of open EO data access for all large disasters.“
“Preliminary inspection of Sentinel-1 interferogram told us vital things about the earthquake instantly. The fact that we have a near-guaranteed response, and we can respond quickly, is a huge benefit from Sentinel-1.”
The 2016 Ecuador earthquake
The Institute for Electromagnetic Sensing of the Environment (CNR-IREA) contributes to the Seismic Hazard pilot and is Center of Competence (CoC) on DInSAR1 for the Italian Civil Protection Department (DPC). In case of major (Mw >6) and shallow depth earthquakes occurring within the Italian territory, CNR-IREA has the mandate to rapidly provide the DPC with DInSAR Earth surface deformation maps, as soon as the first post-seismic SAR acquisition is available.
DPC may also ask for displacement measurements related to earthquakes that occur abroad, in the framework of international collaborations with foreign authorities, as in the case of the earthquake that stroke Ecuador on 16 April 2016 (Figure 1). For this event, on April 17, 2016, the Ecuador government asked assistance to the Directorate-General Humanitarian Aid and Civil Protection of the European Commission. On this basis, and under the coordination of the United Nations, Italy declared the emergency state for the Ecuador earthquake, which allowed Italian logistic support and technical experts to be provided for the evaluation of strategic buildings on site. Within this frame, DPC asked IREA a detailed report on the surface deformations due to the mainshock, which was also forwarded to the Ecuadorian authorities of civil protection. In this case, as in other cases, the generated deformation maps are used by DPC and other DPC CoCs to understand the extension of the area affected by displacement and better focus the activities during the emergency. Moreover, these maps can also be used to model the seismogenic fault in order to increase the knowledge on the earthquake causes.
Innovative online tools and capabilities to support the seismic hazards community
While the growing volume information from Earth-observation satellites offers a unique opportunity for science and applications, it is sometimes difficult to make sure these complex data streams are exploited to their full potential. The Seismic Hazards Pilot closely collaborated with the Geohazards Exploitation Platform (GEP) activity originated by ESA to directly support pilot users exploiting satellite data to assess seismic hazards and in particular users of the GSNL community. The GEP is focusing on the following priorities: support data storage and dissemination; provide online processing for geohazard assessment e.g. terrain motion monitoring based on InSAR or stereo-optical data; support collaborative work (i.e. sharing pilot results) and community building. Seismic Pilot partners used the GEP to access and exploit CEOS data collections of Copernicus Sentinel-1 & Sentinel-2, ALOS-2, Cosmo-SkyMed and TerraSAR-X data, as well as archive ENVISAT and ERS collections. Examples of processing services and ttols that have been used to generate seismic products is Sentinel-1 SBAS, DIAPASON, GAMMA, StaMPS etc.
The GEP supported not only the Seismic Hazards Pilot, but also the Volcano Pilot and other users from the broader geohazards community. Based on its potential, shown during the Seismic Hazards Pilot and its continuous evolution and expansion the GEP will continue to support the WG Disasters and the geohazards community, as part of the CEOS Geohazards Lab. Further information about the GEP can be found on the Geohazards Lab page.
Figure 6. SBAS processing result on the GEP: image shows the mean ground velocity for SE Sicily region, containing Envisat ASAR data (2003-2010), processed by INGV.
“One of the more useful tool in a web-platform such as GEP is the possibility to run multi-temporal interferometric processing, implementing different algorithms such as SBAS or PS, and exploiting the large computing power and storage capabilities present in GEP.”
“The main benefit of technologies such as GEP is that they give users the possibility to perform complex processing of SAR data in a very user-friendly way. The user has immediate access to vast data archives, and the processors available need very little user interaction. In the case of the Kumamoto earthquake, the interferogram was processed on GEP within hours after the availability of the first post-event acquisition.”
A three-year Demonstrator activity started in November 2018, following the successful outcomes of the Pilot. The Demonstrator continues focusing on the objectives of the precursor Pilot activity, but aiming to greater use of EO data and products: (i) effort to evolve from regional to global coverage, and (ii) response to a higher number of earthquakes.
In comparison to the Pilot activity, the demonstrator further aims to:
- Broaden its user base to achieve more impact by continuing to work with the members of the Pilot activity; taking on board new EO practitioners and other (non-expert) geoscience centres with strong links to End users; and reaching more end users.
- Develop a collaborative framework with geoscience centres to promote adoption of EO technology by decision makers, establish a consensus methodology for research product generation and dissemination to decision makers.
- Support local capacity building in coordination with GSNL and other initiatives to broaden the use and acceptance of EO products by geoscience centres and academia and facilitate end users to with their interpretation.
Figure 7. CEOS Seismic Demonstrator map of the world tectonic priorities mask. The mask can be downloaded here.
Moving towards the end of the three-year period, the Demonstrator activity has been proven a success, especially concerning the high demand Very High Resolution (VHR) optical imagery for active fault mapping. This led the Demonstrator leads to propose a second phase of the Demonstrator activity. A proposition is under preparation.
Examples of processed satellite EO products
Figure 8. Example of co-seismic differential interferogram (left image) using Copernicus Sentinel-1 pre-event (25/02/2021) and post-event (09/03/2021) data, corresponding to the ground motion map (right image) of the Tirnavos (Greece) M6.3 earthquake on 03/03/2021. The ground motion map shows a maximum displacement at -38cm. No rupture reached the surface. Contains modified Copernicus Sentinel data (2021), processed by Aristotle University of Thessaloniki (AUTh).
Figure 9. Example of co-seismic differential interferogram (left image) and interferometric coherence map (right image) of the M6.3 earthquake in Tirnavos (Greece), using Copernicus Sentinel-1 pre-event (25/02/2021) and post-event (09/03/2021) data. Wide-spread liquefactions along river basins and distributed surface deformation are depicted by patterns of low coherence (areas in black) nearby the epicentral area. Contains modified Copernicus Sentinel data (2021), processed online on the Geohazards Exploitation Platform (GEP) by Aristotle University of Thessaloniki (AUTh).
Seismic Hazards Demonstrator Implementation Plan