Rapid investigation of co and post-seismic deformation resulting from the 24th August 2016 Amatrice Earthquake (M 6.2)

Lead Research Organisation: University of Leeds
Department Name: School of Earth and Environment

Abstract

At 3:36 AM on the 24th of August a magnitude 6.2 earthquake struck the Amatrice region. The shaking in this event caused nearly 300 deaths and significant damage to the villages distributed across the region. The earthquake ruptured across two faults, the Laga-Amatrice and Vettore faults, which were previously thought to be separate structures that could not rupture in a single event. Our team visited the region days after the event to begin scientific study of this earthquake, investigating the surface expression of the earthquake and installing GNSS equipment that will measure high-resolution motion of the ground continuously for weeks and months following the earthquake. Our team comprises UK and Italian scientists from the University of Leeds, University of Durham, Univeristy of London, Birkbeck University of London, University of Insurbia, the Italian Geological Survey (ISPRA), and Geospatial Research Ltd (Durham). Members of our team who are experts in using satellite data to investigate ground deformation (Durham) processed data in real-time to direct the initial field campaign.

This project will aim to fully characterise the nature of the Amatrice earthquake in terms of what happened during and what is continuing to occur after the seismic event. We will use a variety of techniques including satellite radar measurements and modelling of co and post -seismic deformation, GNSS (Global Navigation Satellite System) measurements of ground deformation, photogrammetry and laser scanning to make high resolution measurements of the surface rupture, detailed field work in the region of the earthquake, and modelling techniques to determine how this earthquake affected stress on the surrounding faults. The work is urgent due to the need to document post-seismic deformation in the weeks and months following the earthquake, and the degrading nature of the surface rupture. This research will allow us to investigate fault connectivity and how linkage develops. We will test hypotheses regarding the role of postseismic deformation after an earthquake that links previously independent structures. Fault linkage typically happens over long geological timescales and has never before been captured before with such a high quality dataset. Our results will be important for incorporating multi-fault rupturing earthquakes into future hazard assessments made in central Italy and globally.

Planned Impact

Direct and short term benefits

A direct impact of this project will be to further develop commercially viable GNSS equipment used for monitoring surface deformation, in collaboration with GRL. GRL has developed continually operating GNSS receivers that are low-cost and quick to deploy. The short-baseline receivers are capable of measuring surface deformation continuously at very high resolution. This is the first time the receivers have been installed immediately after an earthquake, and our project will test and lead to improvements in the rapid deployment of equipment following an event. The GNSS equipment has a broad range of applications, specifically position surveying to provide control for datasets acquired using other geospatial technologies (such as TLS, ground- and UAV-based structure from motion SfM), and the installation of continually operating stations to monitor a variety processes, both geological and anthropogenic.

Our collaborators at ISPRA will directly benefit from the additional datasets we can provide on the characteristics of the rupture based on terrestrial geophysical surveys and satellite data, both measuring the evolving post-seismic slip. Significant post-seismic deformation has the potential to cause further disruption to the ground surface, particularly in the Pescara del Tronto valley where shaking on the steep soft-rock slopes caused landslips and disruption to the road network. Our work mapping the distribution of surface deformation with combined InSAR and GNSS measurements will help to quantify these surface disruptions. These datasets will be incorporated into ISPRA reports on the environmental effects of the earthquake and taken into account when managing repairs in the region.

Indirect and long term benefits

The long term benefit of this project will be to develop a better understanding of the process of fault linkage. This process leads to earthquakes that are much larger than would be expected if the individual strands ruptured independently. Fault linkage is poorly understood, but results from this project will give insight into how links develop. If this process is more likely to occur on Abruzzo faults than previously thought, it will be crucial to incorporate into hazard models for the region, which comprises multiple presumed short fault strands. There is potential for global impact in this study as incorporating multi-fault ruptures into hazard models has been highlighted as one of the key challenges and updates to the recent Uniform California Earthquake Rupture Forecast (UCERF3), which includes a higher likelihood for large events due to the inclusion of multifault ruptures. There are few physical constraints on this process, particularly for normal faults, and therefore our study will be a key dataset for future study of this process and how to integrate it into earthquake hazard models.
 
Description This grant was originally written to investigate the Magnitude 6.2 (M 6.2) Amatrice Earthquake, which occurred on the 24th August, 2016 in central Italy. Following this earthquake, our team immediately began studying the earthquake using field-based surveys, including GPS (GNSS) equipment installed across the causative fault, and satellite radar techniques. The region continued to experience strong and damaging earthquakes, with a M 6.1 on the 26th October, and finally a 6.6 on the 30th October. The hazard was therefore ongoing, and we continued to investigate this related seismic activity, in the field and remotely. Our primary results are as follows:

(1) GNSS: Our sensors were collecting data when the 30th October event occurred. As a result, we measured the near-field motion of the ground surface during a large earthquake. Our sensors recorded their positions every one second, and therefore we could see how slip at the earthquake surface was manifested in the earthquake. This allowed us to estimate how fast the rupture propagated, and also is currently informing our modelling of what happened during the earthquake at depth on the fault itself. The work has also contributed to the development of GNSS equipment for monitoring purposes in other earthquake prone regions (New Zealand) and in industrial applications.

(2) Surface rupture pattern: When an earthquake occurs on the continents, it rips the ground apart and leaves behind a surface rupture. The location, pattern, and extent of this rupture can inform us on what happened during the earthquake, including how the rupture grew in space and time, and why it stopped. Our work on this grant fed into a large scale rupture map coordinated by the EMERGEO working group at the National Institute for Geophysics and Volcanoes in Italy. This map has been used by many scientists studying the earthquakes, and data was immediately fed into decisions made by emergency workers in the aftermath of the earthquakes. Our key findings are that the rupture was incredibly complicated in all three events, which is not expected in relatively small earthquakes. Many faults that were known 'geologically' were activated by the earthquake, placing confidence in how geological fault maps can be used in determining future earthquake hazard.

(3) What happened during the earthquakes? Our work combining the above efforts with satellite radar data that measured how the ground moved during the earthquake has allowed us to hypothesize how and why the sequence evolved as it did. Our results show that earthquake rupture was impeded by some cross-cutting structures at depth, which were previously unknown to exist. However, the earthquakes also cut across structures that were thought to act to stop the rupture propagation. Our understanding of this sequence is important for future hazard in Italy and on other complicated fault systems globally, as we can show that (1) the hazard due to earthquakes may continue long after the first seismic event in a sequence and (2) the structure of fault systems at depth is important for earthquake propagation.

(4) How does the ground deform during and after the earthquake, particularly near the fault? We collected an extensive dataset of Terrestrial Laser Scans, from which we can make high resolution (e.g. <1 cm) maps of the motion of the ground around the fault. We have data that constrain the motion both in a large (M 6.6) earthquake and in timesteps following the event. Our major finding thus far is that vertical and horizontal movement in the earthquake may be partitioned, such that the vertical movement mostly occurs on the fault, whereas the horizontal motion may be distributed up to several m's away from the fault. This has important implications for investigating earthquakes that have occured in the geological past using paleoseismic techniques.
Exploitation Route Our contribution to the rupture map of this earthquake should be used by the Italian Civil protection to continue to monitor hazard associated with surface ruptures in the area. Ultimately this map, and the work we have done to better understand what happened during these earthquakes (published in Walters et al., 2018, EPSL) will help to estimate future hazard in central Italy. Our work understanding these earthquakes will also be relevant for earthquake scientists and policy makers globally, as we have made advances in our understanding of how and why earthquakes occur and propagate at depth, particularly in earthquake sequences on complicated fault networks.
Sectors Construction,Government, Democracy and Justice

 
Description Our field research funded by this grant contributed to mapping of surface ruptures in the immediate aftermath of each of three earthquakes. We then fed our data directly to the EMERGEO team in central Italy, which is the earthquake response team within the INGV (the Italian Geophysical survey), who ultimately have responsibility to inform the Italian Civil Protection with updates on the understanding of the earthquake. EMERGEO was open to international scientists and therefore we were able to contribute to their datasets. We also worked with the British spin-out company, Geospatial Research Ltd (also a project partner) and deployed their short-baseline GNSS equipment in the first instance of monitoring and measuring earthquake related surface deformation. What we learned as a team in this deployment contributed to advances in deploying this technology, thus benefiting industry and having an impact on their future development of the equipment and processing. During the earthquake sequence, members of our team (myself in particular) conducted numerous interviews with the media (radio, TV, and print/web), keeping the public up to date with scientifically accurate information about the sequence. This earthquake sequence was relevant to the British public perhaps more so than other similar events because it occurred in Europe and the region is a holiday destination for British tourists.
First Year Of Impact 2016
Sector Government, Democracy and Justice,Other
Impact Types Societal,Economic,Policy & public services

 
Title Opentopography.org digital topography dataset of the 2016 Norcia earthquake 
Description Two datasets are available that document the pre- and post- earthquake topography along the surface rupture of the 2016 M 6.6 Norcia earthquake. These are hosted on the opentopography.org website and anyone can access these data. They are also associated with a relevant publication. The doi's are: https://doi.org/10.5069/G9CV4FV2 = 2016 Norcia Earthquake (Italy), Mt Bove Fault - Post-earthquake https://doi.org/10.5069/G9JQ0Z4H = 2016 Norcia Earthquake (Italy), Mt Bove Fault - Pre-earthquake 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Impact These data resulted in a paper that has just been published in pre-print form in the journal Geophysical Research Letters. It has only recently been published so we do not know of any impacts as of yet. The data should be an important future baseline for monitoring the surface rupture. 
URL http://opentopo.sdsc.edu/dataspace/dataset?opentopoID=OTDS.022019.32633.1
 
Description The EMERGEO working group hosted by the INGV (National Institute of Geophysics and Volcanology, Italy) 
Organisation National Institute for Geophysics and Volcanology (INGV)
Country Italy 
Sector Public 
PI Contribution During the seismic crisis in central Italy in 2016, the EMERGEO working group was tasked with documenting and evaluating the seismic effects of the surface rupturing earthquakes, and using this information to advise emergency management. When the M6.6 30th Oct earthquake occurred, the EMERGEO working group became the 'Open EMERGEO' working group, and reached out to international colleagues and colleagues from Italian Universities, to work together in documenting the extensive surface effects. Our team was in the area at the time of this event, and immediately began documenting ruptures and updating the EMERGEO team through our colleagues there and in ISPRA/University dell'Insubria (already collaborators on this grant). Our field data ultimately contributed to the final dataset collated by EMERGEO, which has been published and is used for continued hazard monitoring in the region. We also made terrestrial laser scans of paleoseismic trenches analysed by the EMERGEO group (and shared this data with EMERGEO). Results from this work which will ultimately be used to define the historical record of the causative faults in updated hazard maps for the area.
Collaborator Contribution The EMERGEO working group has fully shared all data collected by all members of the group, making it possible to make detailed models of the event for geodetic modelling. Our collaborators in EMERGEO also arranged for permission to access the 'red zone' - the area affected most by the earthquakes, which entirely facilitated the collection of field-based datasets in funded by this grant.
Impact Publications: https://doi.org/10.1080/17445647.2018.1441756
Start Year 2016
 
Title short baseline GNSS 
Description In collaboration with our partner Geospatial Research Ltd (GRL), we helped to develop the application of low-cost Global Navigation Satellite System (GNSS) receivers. These receivers have a short baseline and thus can measure accurate surface displacements (at a rate of 1 Hz) at a relatively cheap cost and easy deployment. In this project we for the first time deployed units on an active fault system. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2016 
Impact Our work led to deployment of low-cost receivers following the 2016 Kaikoura earthquake in New Zealand (with improvements in the methods following our work), and further commercial contracts for GRL. 
 
Description Interview for national news 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Myself and my team conducted many media interviews following the earthquake on the 30th October, 2016, as scientific experts on the subject. Several interviews were reported on the BBC News website (conducted by Jonathan Amos), and I conducted interviews with BBC Breakfast, BBC World Radio, CNN, and BBC Radio Leeds. No known impacts but the interviews educated the public on the ongoing seismicity in Italy. Myself and other members of the team have subsequently been invited for expert opinions on other earthquakes globally.
Year(s) Of Engagement Activity 2016
URL http://www.bbc.co.uk/programmes/p04dmkmv