Departamento de Física

URI permanente para esta comunidadhttp://10.0.96.45:4000/handle/11056/14434

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A first estimation of tsunami hazard of the Pacific coast of Costa Rica from local and distant seismogenic sources
(Springer, 2021-06-04) Chacon-Barrantes, Silvia; Arozarena-Llopis, Isabel
Costa Rica has been affected by several local and distant tsunamis in the past, but the historical information is scarce and incomplete. Its Pacific coast stretches for over a thousand kilometers, and tsunami hazard has never been evaluated for its full extent. Numerical modeling of tsunami propagation and inundation is a useful tool to assess tsunami hazard, particularly in cases with limited historical information available. Here, we perform a first estimation of tsunami hazard for the Pacific coast of Costa Rica from seismogenic sources, by numerical propagation of 57 local and distant tsunamis to a depth of 20 m. The results of our study identified tsunami sources that are particularly threatening for Costa Rica and determined locations with higher tsunami hazard. For the analysis, the Pacific coast of Costa Rica was divided into segments and subsegments based on differences in continental slope morphology. Subsegments with higher tsunami heights were Southwest Nicoya Peninsula and West Osa Peninsula, and in a lesser extent North Guanacaste, North Nicoya Peninsula, and Central Pacific. Regions with long and gentle slopes and narrow continental shelf were affected by higher tsunami waves, due to more efficient tsunami energy transmission to the shelf and reduced energy loss while traveling through a narrow shelf. On the opposite, steeper continental slopes reflected most of the tsunami energy, causing smaller tsunami heights nearshore, regardless of the shelf width. Nevertheless, other effects played a major role, like curved coastlines that focused tsunami energy, wave refraction, interference, and trapped edge waves. Distant tsunamis dominated the threat, with tsunamis coming from the Tonga-Kermadec and the Colombia-Ecuador Trenches causing the greatest heights due to directivity, and arrival times of about 15 h and 75 min, respectively. Local tsunamis had short arrival times but a localized impact, mainly at the shoreline in front of the generation region but were also affected by tsunami focusing, wave refraction, and edge waves. Outer rise and Osa sources caused the lowest impact within local sources. These results provide a guide for emergency planners to prioritize coastal locations and tsunami sources for tsunami preparedness actions and warning protocols.
“Impact of the tsunami caused by the Hunga Tonga–Hunga Ha’apai eruption in Costa Rica on 15 January 2022”
(Springer, 2023-05-12) Chacon-Barrantes, Silvia; Rivera Cerdas, Fabio; Murillo Gutiérrez, Anthony
Hunga Tonga–Hunga Ha’apai had a large eruption (VEI 5–6) on 15 January 2022, which caused a tsunami recorded in all ocean basins. Costa Rica has made many advances in tsunami preparation over the past 9 years since the creation of SINAMOT (Sistema Nacional de Monitoreo de Tsunamis, National Tsunami Monitoring System), both on watch and warning protocols and on community preparedness. For the Hunga Tonga–Hunga Ha’apai event, the government declared a low-threat warning, suspending all in-water activities, even though the country did not receive any official warning from PTWC (Pacific Tsunami Warning Center) due to the lack of procedures for tsunamis generated by volcanoes. The tsunami was observed at 24 locations on both the Pacific and Caribbean coasts of Costa Rica, becoming the second most recorded tsunami in the country, after the 1991 Limon tsunami along the Caribbean coast. At 22 of those locations along the continental Pacific coast, observations were made by eyewitnesses, including one collocated with the sea level station at Quepos, which registered the tsunami. At Cocos Island (~ 500 km southwest of the continental Costa Rica, in the Pacific Ocean), several eyewitnesses reported the tsunami at two locations, and it was recorded at the sea level station. The tsunami was also recorded at the sea level station on the Caribbean coast. The tsunami effects reported were a combination of sea level fluctuations, strong currents, and coastal erosion, proving that the response actions were adequate for the size of the tsunami. Tsunami preparedness and the largest waves arriving during a dry season Saturday afternoon allowed the large number of eyewitness reports. This event then increased tsunami awareness in the country and tested protocols and procedures. Still, many people along the coast were not informed of the tsunami during the alert due to their remote location, the short notice of the warning, and a lack of procedures for some communities. There is thus still much work to do, particularly about warning dissemination, a direction in which communities should take an active role.
New records of historical tsunamis obtained from Costa Rican newspapers
(American Geophysical Union, 2020-12-14) Chacon-Barrantes, Silvia; Murillo Gutiérrez, Anthony; Rivera Cerdas, Fabio
Costa Rica has few records of historical tsunamis, due to traditionally low populated coasts and moderate tsunami potential, among other reasons. As part of the writing of the first tsunami catalog of Costa Rica, the authors performed an extensive search of reports that can be associated with tsunamis on newspapers from 1851 to 1992, at the Costa Rica National Library database (SINABI, 2020). The dates searched were related to 25 earthquakes originated in Costa Rica, Nicaragua and Panamá, from 1851 to 1992, with Mw > 6.0 or MMI > VII. Also, four remote tsunamis were considered: 1906 Colombia, 1952 Kamchatka, 1960 Chile and 1964 Alaska. For each event, we searched newspapers starting from the day after the earthquake until 15 days after. We found reports that refer certainly to tsunamis for the 1906 Colombia and 1941 Osa (5 December) earthquakes. For both tsunamis there were records from witnesses at other locations in Costa Rica, and the 1941 tsunamis (5 and 6 December) were the first recorded in tide gauges in Costa Rica. We also found entries on newspapers that might refer to tsunamis but cannot be conJrmed, linked to 1916 Papagayo, 1916 Bocas del Toro and 1924 Tárcoles earthquakes. Bocas del Toro tsunami was registered in Panamá; the other two earthquakes were caused by subduction in the Middle America Trench and thus very likely caused tsunamis; although there are no records linked to them. These three events were classified as probable tsunamis for the catalog. For the 1905 Nicoya Gulf earthquake, we found a reference of coastal landslides that might be related to the tsunami experienced in Cocos Island. Here we geolocalize the entries found and discuss them in terms of what is known from the respective earthquake and tsunami. We could not Jnd any information in the newspapers related to the tsunamis: 1950 Nicoya, 1952 Kamchatka, 1960 Chile, 1964 Alaska,1983 Golfito, 1990 Cóbano, 1991 Valle de la Estrella and 1992 Nicaragua, despite they were recorded at tide gauges and/or observed by witnesses. This was particularly unexpected for the tsunamis of 1991 and 1992, as they were the largest recorded at Caribbean and Pacific coasts of Costa Rica, respectively. The reports of abnormal sea level changes in newspapers provided a valuable complement to the records from other sources, and for some events are the only record available.
Numerical Simulations of the 1991 Limón Tsunami, Costa Rica Caribbean Coast
(Pure and Applied Geophysics vol.174 2945-2959 2017, 2017) Chacon-Barrantes, Silvia; Zamora, Natalia
The second largest recorded tsunami along the Caribbean margin of Central America occurred 25 years ago. On April 22nd, 1991, an earthquake with magnitude Mw 7.6 ruptured along the thrust faults that form the North Panama ́ Deformed Belt (NPDB). The earthquake triggered a tsunami that affected the Caribbean coast of Costa Rica and Panama ́ within few minutes, generating two casualties. These are the only deaths caused by a tsunami in Costa Rica. Coseismic uplift up to 1.6 m and runup values larger than 2 m were measured along some coastal sites. Here, we consider three solutions for the seismic source as initial conditions to model the tsunami, each considering a single rupture plane. We performed numerical modeling of the tsunami propagation and runup using NEOWAVE numerical model (Yamazaki et al. in Int J Numer Methods Fluids 67:2081–2107, 2010, doi: 10.1002/fld.2485 ) on a system of nested grids from the entire Caribbean Sea to Limo ́n city. The modeled surface deformation and tsunami runup agreed with the measured data along most of the coastal sites with one preferred model that fits the field data. The model results are useful to determine how the 1991 tsunami could have affected regions where tsunami records were not preserved and to simulate the effects of the coastal surface deformations as buffer to tsunami. We also performed tsunami modeling to simulate the consequences if a similar event with larger magnitude Mw 7.9 occurs offshore the southern Costa Rican Caribbean coast. Such event would generate maximum wave heights of more than 5 m showing that Limo ́n and northwestern Panama ́ coastal areas are exposed to moderate-to-large tsunamis. These simulations considering historical events and maximum credible scenarios can be useful for hazard assessment and also as part of studies leading to tsunami evacuation maps and mitigation plans, even when that is not the scope of this paper.

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