ATTAC

Scientists from the SED are working with local monitoring agencies from the region to build Earthquake Early Warning (EEW) across Central America. This multi-phase project is funded by the Swiss Agency for Development and Cooperation (SDC) at the Federal Department of Foreign Affairs (FDFA). In Phase 1 (2016-2017), SED worked with colleagues at INETER to evaluate the potential for EEW and to implement a prototype EEW system in Nicaragua. In Phase 2 (2018-2021), this prototype system was extended to include monitoring agencies in 3 additional countries - OVSICORI-UNA in Costa Rica, MARN in El Salvador, and INSIVUMEH in Guatemala. 70 EEW-ready strong motion accelerometers were purchased and deployed in the region. We further began to explore how a public EEW could be implemented, with EEW messages being integrated in the the emerging Digital-TV infrastructure as well as with a cellphone app developed within the project. In Phase 3 (2022-2024), we transition to operational EEW and public EEW messages using this cellphone app, and in the case of Guatemala City, an urban siren system. On 14 June 2023, the first public version of the cellphone app was released in Costa Rica.

The region suffers from large tsunamigenic earthquakes generated along the subduction zone, and also moderate crustal earthquakes that have in the recent past produced heavy damage, such as the M6.2 1972 earthquake that devastated Managua. The subduction zone events are often characterized by slow rupture velocity (the M7.7 1992 earthquake - the first slow earthquake ever documented - and most recently a M7.3 in 2014)

Earthquake Early Warning (EEW) is a tool that can rapidly characterize on-going earthquakes, and potentially provide seconds to 10s of seconds notification of impending strong shaking in advance of its occurrence. EEW can play an important role as part of a seismic risk reduction program, which is critical in the Central American region that has such a high seismic hazard. Additionally, making a seismic network capable of operating and maintaining an EEW system requires the network to achieve the highest standards in network performance - including station quality, speed and reliability of data communications, and robustness of the seismic network hub that runs the EEW software. Optimal network performance is also critical for other applications such as tsunami warning, volcano monitoring, and enables downstream scientific studies, eg on local Earth structure.

EEW can work in Central America because the seismic networks are relatively dense and data sharing is well-established and effective - necessary as earthquakes can have impacts beyond a single country. On 9 June 2016, just weeks after the first software was installed and before efforts to optimise had begun, a shallow M6.3 event occurred on the border with El Salvador that was detected by our system after 29s. Though far from the delay time required for operational EEW, this did demonstrate the promise of the existing infrastructure. With the current seismic network and optimised system, we typically can provide first EEW alerts within 8-12s for shallow on-shore earthquakes. This corresponds to a blind zone on the order of 20-30km around the epicenter where no advanced warning will be available. Outside the blind zone, for large earthquakes, this type of EEW can provide warning in advance of the strongest shaking for areas that will experience shaking of intensity VI on the Modified Mercalli Scale.  

Transfer of EEW capacity from SED to Central American Institutes is feasible because each agency use the same basic software for seismic network monitoring - SeisComP3 - that the SED itself relies on, and on top of which we have added EEW capability. SED use 2 standard algorithms to provide EEW - the Virtual Seismologist and the Finite Fault Detector. We also have been using the EEW Display (EEWD) to deliver desktop alerts to early adopters and testers.