Why are geohazards important?
Earthquakes represent one of the world's most significant hazards in terms both of loss of life and damages, and are also responsible for many other related fatalities and damages through tsunamis, which are triggered by earthquakes. In the first decade of the 21st century, earthquakes accounted for 60 percent of deaths from natural disasters, according to the United Nations International Strategy for Disaster Reduction (UNISDR). In 2010 alone, more than 225,000 people were killed. Even when loss of life is reduced, the economic impact can be devastating. The M9.0 Tohoku Japanese earthquake in 2011 killed 100 people, but nearly 20,000 lost their lives in the subsequent tsunami, and losses of the overall event are estimated at over $360 billion.
Science users require satellite EO to support mitigation activities designed to reduce risk. They are carried out before the earthquake occurs, and are presently the only effective way to reduce the impact of earthquakes on society. Short-term earthquake prediction today offers little promise of concrete results. The assessment of seismic hazard requires gathering geo-information for several aspects: the parameterization of the seismic sources, knowledge of historical and instrumental rates of seismicity, the measurement of present deformation rates, the partitioning of strain among different faults, paleo-seismological data from faults, and the improvement of tectonic models in seismogenic areas.
Operational users of seismic risk management do have needs for geo-information to support mitigation, although the need for situational awareness during response often receives more attention. Satellite EO can contribute by providing geo-information concerning crustal block boundaries to better map active faults, maps of strain to assess how rapidly faults are deforming, and geo-information concerning soil vulnerability to help estimate how the soil is behaving in reaction to seismic phenomena. On an emergency basis, the first information needed after a large earthquake occurs is an assessment of the extent and intensity of the earthquake impact on man-made structures, immediately after which it becomes important to formulate assumptions on the evolution of the seismic sequence, i.e. where local aftershocks or future main shocks (on nearby faults) are most likely to occur.
A range of EO-based techniques have been developed to support the mitigation of earthquakes, for crisis management and for the analysis of the seismic risk, for instance:
- The use of high-resolution optical and topographic data sets for investigating tectonic geomorphology, paleo-seismology etc., especially for forensic investigations of previous major earthquakes.
- High resolution optical/radar image matching for deformation.
- SAR Interferometry (InSAR), in particular the Persistent Scatterer Interferometry (PSI) technique, to provide precise terrain deformation concerning seismic risk.
In May 2012, the European Space Agency and the GEO Secretariat convened the International Forum on Satellite EO for Geohazards now known as the Santorini Conference. The event was the continuation of a series of international workshops such as those organized by the Geohazards Theme of the Integrated Global Observing Strategy Partnership, and initiatives such as the Geohazard Supersites & Natural Laboratories (GSNL). In Santorini the seismic community has set out a vision of the EO contribution to an operational global seismic risk program. In 5 to 10 years' time, EO could provide fundamental new observations of the seismic belts - around 15% of land surfaces.
At that same Santorini Conference, the volcanic community identified priorities for satellite support to geohazards. In the long-term, the community aims to monitor all 1500 Holocene era volcanoes on a global basis, a dramatic increase from the roughly 10% that are monitored now using both satellites and terrestrial sensors. The pilot believes this can be achieved incrementally after the pilot demonstrates regional success, through:
- global background observations at all Holocene volcanoes;
- weekly observations at restless volcanoes;
- daily observations at erupting volcanoes;
- development of novel measurements;
- 20-year sustainability;
National and Regional Civil Protection authorities, Seismological centers, and National and Local authorities in charge of seismic risk management activities are concerned with the phases of prevention, preparedness, early warning, response, recovery, rehabilitation and reconstruction. Beyond operational users with a mandate in seismic risk management, there is a range of geoscience users focused on the scientific use of data with the main goal of understanding the physics that drive earthquakes, thereby improving our ability to characterize, understand, and model seismic risk.
The GEP and CEOS Pilots:
The Geohazards Exploitation Platform or GEP aims to support the exploitation of satellite EO for geohazards. It follows the Supersites Exploitation Platform (SSEP), originally initiated in the context of the Geohazard Supersites & Natural Laboratories initiative (GSNL). The geohazards platform has been expanded to address broader objectives of the geohazards community. In particular it is a contribution to the CEOS WG Disasters to support its Seismic Hazards Pilot and terrain deformation applications of its Volcano Pilot. The geohazards platform is sourced with elements – data, tools, and processing - Optical and Radar – relevant to the Geohazards theme.
One of the core user communities for the GEP is the group of users and practitioners working on the CEOS Seismic Hazards Pilot, a three-year demonstration project of the Committee on Earth Observation Satellites to showcase how satellite EO can be applied to seismic hazard research. The Seismic Hazards Pilot is pursuing three objectives:
- Support the generation of globally self-consistent strain rate estimates and the mapping of active faults at the global scale by providing EO InSAR and optical data and processing capacities to existing initiatives, such as the iGSRM (i.e. wide extent satellite observations)
- Support and continue the GSNL for seismic hazards and volcanoes (i.e. satellite observations focused on supersites)
- Develop and demonstrate advanced science products for rapid earthquake response (observation of earthquakes with M>5.8)
CEOS is also coordinating a Volcano Pilot, which uses the GEP to exploit data in much the same way. The objectives of the Volcano Pilot are:
- Demonstrate the feasibility of integrated, systematic and sustained monitoring of Holocene volcanoes using space-based EO;
- Demonstrate applicability and superior timeliness of space-based EO products to the operational community (such as volcano observatories and VAACs) for better understanding volcanic activity and reducing impact and risk from eruptions;
- Build the capacity for use of EO data in volcanic observatories in Latin America as a showcase for global capacity development opportunities.
Today the GEP has primary focus on mapping hazard prone land surfaces and monitoring terrain deformation. It allows users to access and exploit large collections ENVISAT ASAR and ERS SAR data hosted in the ESA clusters and in ESA’s Virtual Archive. A large collection of ENVISAT ASAR and ERS SAR are available in the platform. In 2014 an additional 40+ Terabytes of ERS and ASAR data was added in response to requirements of the CEOS Pilot on Seismic Hazards. The GEP is also be used to gradually access Sentinel-1A data. The activity also intends to support access to other EO missions’ data than from ESA such as from other space agencies and mission owners and operators.