Rapid deployment of a seismic array in Ecuador following the April 16th 2016 M7.8 Pedernales earthquake

This project will rapidly deploy a seismological network at the southern end of the April 16th 2016 M7.8 Pedernales earthquake in Ecuador (Objective 1). Our project partners are currently deploying seismological stations in the central (GEOAZURE, IRD, France) and northern (IRIS, USA) regions of the fault zone. The seismological network will record earthquake activity continuously for a period of 10 months, with a service after 5 months. The dataset obtained, which will be openly shared among our project partners and the scientific community will provide unprecedented resolution on imaging aftershock activity on the subduction interface. Once collected after 5 and 10 months, the continuous data will be processed to detect earthquakes which will be located while jointly determining high-resolution 3D velocity structure in this tectonically complex subduction zone. By interpreting the spatial and temporal distribution and migration of aftershock activity we will gain valuable insight into the stress conditions at the subduction interface. Additional analysis of attenuation that the seismic waves have undergone will, when jointly interpreted with the P-wave and S-wave velocity structure, will provide information as to the chemical and mineralogical nature of the subduction zone and processes.

In order to interpret the seismological data in terms of the stress and strain changes that have taken place before, during and after the M7.8 earthquake, we will use satellite interferometry to determine, for the first time, a multi-temporal InSAR time series (Objective 2). This will be done by processing multiple satellite images of the zone, from 6 months before to 12 months after the earthquake. From these images we can ascertain the ground deformation. The data collected will allow us to bring together interdisciplinary information to interpret the state of stress and its evolution in this poorly studied and instrumented part of the world. Finally, using all data and interpretations gathered we will address the question of whether the southern region of the fault zone is likely to rupture, and what the likely response of nearby volcanic zones will be to changes in the regional stress field.

The results obtained from this project will have far reaching impacts, both direct:
- seismic imaging of a previously unseen subduction zone;
- insights in to subduction zone processes pre-, co- and post seismically;
- understanding the state of stress and its spatial and temporal redistribution as a result of the M7.8 earthquake.
- development of a research collaboration (UK, France, USA) which will share and work together to interpret data.
- establishing links with the Instituto Geofisico for current and future cooperation.

And indirect:
- improved real-time seismic monitoring and interpretation;
- improved geodetic seismic monitoring using satellite radar interferometry over densely vegetated areas;
- better understanding of the threat of the seismic gap to the south: is another large earthquake likely in the near future?
- Improved seismic safety and design - based on the interpretation of the state of stress, the authorities will be in a position to invest (or not) in seismic retrofitting if it is thought that the zone to the south presents a threat.

Short term beneficiaries
Potential beneficiaries of this information are varied, from governmental institutions to the general public. The principal short-term non-academic benefit lies in the application of the models developed for improving earthquake location and monitoring (government/institutional) in the region. Routine localization and monitoring of earthquakes is a critical aspect of seismic observatory practice - and ultimately to civil defence/disaster management. Particularly in the case of real-time-monitoring and alerting during episodes of increased activity, seismic observatories have a significant amount of public and governmental organisation interaction.
NERC DTP students, and students at the University of Liverpool will also see a short term benefit - being able to work on, and see at first hand the results from a unique dataset that has the potential to answer some of the great scientific questions, such as how do subduction zones work, and the what is the state of stress in the crust?

Long term beneficiaries
We identify long term beneficiaries as the government and institutions in Ecuador which will use the physical and conceptual models to inform their long term seismic hazard and risk mitigation strategies. Downstream this has a benefit to the general population of Ecuador, which will benefit from a safer living environment due to seismic retrofitting, if deemed necessary. We plan to establish two NERC DTP projects that use the data and results from this project. This will benefit young scientists and give them an ideal start in their academic careers.