Estudio de campo del tsunami de Costa Rica del 22 de abril de 1991

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doi:10.15517/rgac.v0i65.47001

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Artículo • Rev. Geol. Amér. Central (65) • July-Jun 2021 • https://doi.org/10.15517/rgac.v0i65.47001 linkcopiar

Estudio de campo del tsunami de Costa Rica del 22 de abril de 1991

Autoría SCIMAGO INSTITUTIONS RANKINGS

Resumen

Después del terremoto de Limón, Costa Rica del 22 de abril de 1991 (Mw 7.7) se observó un pequeño tsunami (magnitud, m~ 1) a lo largo de la costa caribeña de Costa Rica y Panamá. Este informe resume las observaciones de testigos oculares de 26 sitios a lo largo de 150 km de costa afectada desde río Matina, Costa Rica hasta Bocas del Toro, noroeste de Panamá, así como mareogramas registrados en Panamá, Puerto Rico y las Islas Vírgenes. No se emitieron advertencias de emergencia antes de que ocurriera el tsunami. Aunque se reportaron pocos o ningún daño a la propiedad relacionada con el tsunami, dos o más ahogamientos fueron atribuidos al tsunami. La altura máxima de las olas fue de 2 a 3 m, y la inundación y las inundaciones costeras se extendieron hasta 200 m tierra adentro en algunos lugares. Tanto la elevación costera cosísmica como la presencia de arrecifes marinos parecen haber proporcionado protección contra los principales efectos del tsunami en algunas zonas costeras. En otros lugares, los efectos de las olas se amplificaron en las desembocaduras de los ríos debido a la compactación diferencial de sedimentos no consolidados. La deposición generalizada de arena de tsunami cerca de la frontera Costa Rica-Panamá en 1991 es similar a la deposición asociada con el terremoto y tsunami del 7 de mayo de 1822.

Palabras clave: tsunamis del Caribe; terremoto y tsunami de Costa Rica de 1991; cuestionario de tsunami; registros y observaciones de campo; Limón; Bocas del Toro

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Universidad de Costa Rica Universidad de Costa Rica. Campus Universitario Rodrigo Facio, San Pedro, San José, CR, 214-2060, 2511-0000, 2511-4000 - E-mail: pdenyer@geologia.ucr.ac.cr

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Tsunami magnitude, m*	Significance
-1	h_max ~ 1/2 m; minor tsunami
0	h_max ~ 1 m; no damage
1	h_max ~ 2 m; house damage along coastal areas, ships washed ashore
2	h_max ~ 4 - 6 m; some destruction of houses, considerable loss of life
3	h_max ~ 10 - 20 m; damage area along the coast about 400 km
4	h_max greater than 50 m; damage area along the coast more than 500 km
*Tsunami magnitude, m = log₂h_max, where hmax is the maximum height in meters measured at a coast 10-300 km from the tsunami origin (Iida, 1970)

Site	Location	N Lat º	W Long º	Description	Runup Height (cm)*	Coseismic Uplift (cm)*	Site Characteristic
	Costa Rica
1	Boca del Rio Matina	10.12º	83.19 º	The water retreated 400 m followed by large waves that flooded 180 m inland. Two drownings occurred in the canal near Matina. Widespread liquefaction. Dead fish were observed following the tsunami.			Beach/ River Mouth
2	Boca del Pantano	10.07º	83.16º	The water first receded ~100 m and then returned within 3 min without flooding.			Beach
3	12 Millas de Moin	10.07º	83.16º	Two minutes after the earthquake, a 2 m wave flooded 30 to 70 m inland. Sand movement.			Beach
4	6 Millas de Moin	10.00º	83.10º	The water slowly retreated about 20 m	135		Beach
5	Moin	10.00º	83.08º	The water retreated about 200 m. A sea wave overtopped 3 m high dikes in the Moin River.		125-140	Harbor/ River Mouth
6	Westfalia	9.94º	83.00º	The water retreated about 200 m and returned to the shoreline without appreciable runup or flooding. Sand movement.	130	74	Beach
7	Cahuita	9.74º	82.84º	The sea receded 75 m then returned slowly to a level lower than previous. Dead fish were observed.		38	Reefs
8	Puerto Viejo	9.66º	82.76º	The sea receded 100 m followed by a large wave, receded again and was followed by a large wave with 30 -70 m runup. Sand movement and dead fish were also noted.	155	38-45	Reefs
9	Final de Cocles	9.64º	82.72º	The sea receded 20 m then returned slowly over a 5 - 6 min period with no runup.		29-54	Beach and Cliffs
10	Punta Uva	9.64º	82.69º	Water retreats 400-600 m	200	40-45	Beach
11	Manzanillo	9.63º	82.66º	The sea receded 180 m and returned in 5 min to flood 30 to 70 m inland. Sand movement and 1.5 m sand mounds were deposited.	83-130	30-40	Beach
12	Gandoca	9.60º	82.60º	The sea receded 300 m in 5 min and returned to flood about 70 m inland. Sand Movement.	125	30-40	Beach
	Panama
13	San-San Natural Refuge	9.54º	82.53º	Tsunami waves deposited a great deal of sand on the beach near the mouth of the San-San River, a wildlife refuge near the Costa Rica border, creating dunes which covered numerous turtle nests with approximately 1 m of sand and caused a decrease in the number of newborn turtles (see Fig. 6).			Beach
14		9.51º	82.49º				Beach
15	Playa de Julio Abrego	9.43º	82.41º	A farmer reports that the before the quake occurred, the sea was very quiet. Minutes after the event the sea receded between three and six times. The last wave was the largest and the water penetrated 100 m inland. The NE-SW trend of fallen palm trees and other types of vegetation surrounded by sand and onshore flooding is seen in Fig. 4.			Beach
16	Changuinola River/ Tiribibi Pt.	9.42º	82.38º	Figure 5 shows the onshore flooding in this area and a zone of brown grass and vegetation parallel to the coastline. Sand deposition and fast currents			Beach
17	Lime Point (Boca del Drago)	9.41º	82.33º	Every person interviewed at this location reports that the sea was very quiet before the earthquake; but one-half to one hour before the event the sea was unusually warm. The sea receded approximately six times out to the coral reefs (approximately 100 m from shore) which looked like a stone wall. All six times the sea returned with a great roar and noise. The last wave was estimated to be 2 m high and flooded parts of the coastal road. This estimate was verified in the field by one of the authors (E. Camacho). The following day, the Boca del Drago passage had many dead fish floating in the water. Sea recedes 6 times and exposed reefs. Flooded coastal roads			Reef
18	West Knapp Hole	9.41º	82.33º	This site is located in the coast facing Almirante Bay. Before the earthquake, the sea was calm. Minutes after the quake, there was a great turbulence in the sea, similar to rapids of the strong current of a river. The strong current flooded from 5 to 10 m of the beach. Great turbulence with strong currents observed after earthquake. 5-10 m runup			Beach on Almirante Bay
19	Ground Creek	9.40º	82.31º	The sea was quiet before the quake. Water receded several times and returned as a strong river current approximately 0.6 m high, which deposited many fish along the banks of the creek which were flooded in some parts up to 10 m inland. Water receded, returns as strong current 0.6 m high. 10 m runup			Beach on Almirante Bay
20	Punta Cauro	9.43º	82.32º	This site faces the Caribbean Sea. The sea was quiet before the earthquake. The sea receded five times and returned making great noise. One witness left some clothes drying on a rock some 2 m or more above the surface of the water near a cliff. After the high waves ceased, she returned to get her clothes, and discovered they had been taken by the waves. She thinks the last wave was the one that took her clothes. A few days later, she recovered her clothes, which may have been brought back by the strong sea currents which run parallel to the coast in this area. Water receded 5 times and the last wave was ~ 2 m high.			Beach with Cliffs
21	Boket Bay	9.43º	82.30º	This site faces the Caribbean Sea. Ten to fifteen minutes after the earthquake, a 2.5 to 3 m high wave was observed from a house standing on top of a hill.2.5-3.5 m wave 10-15 min after earthquake.			Cove
22	Bocas del Toro	9.34º	82.25º	The sea was quiet before the earthquake. Ten minutes after the event, the sea receded approximately 400 m from the cove facing the town. The sand bar, Las Delicias (Grassy Bank) which is usually covered by 0.6 to 0.7 m of water, emerged and remained subareal from 5-7 minutes. After this period, several 0.6 to 0.7 m high waves started to enter the cove with great force. The water was full of sediment and flooded 100 to 150 m inland, mainly on the north part of town, which is located in an extremely flat area. Water receded 10 min after earthquake and exposed an offshore sandbar usually 0.6 m deep. Wave runup 10-15 m.			Reef
23	Nancy Key	9.33º	82.22º	As observed from Hospital Point, 10 to 15 minutes after the earthquake, the sea receded several times and returned as a strong river current from Bocas del Toro passage. Water receded several times and returned as a strong current.			Point
24	Isla San Cristobal	9.29º	82.27º	In the northwest portion of the island, in the mouth of Paloma Creek, the sea receded several meters for approximately 45 minutes. Many fish got trapped in the dry terrain. The water returned as a slow wave recovering the areas that had emerged minutes before. .Sea recedes several meters for 45 min, water returns as a slow wave.			Creek
25	Isla Carenero	9.34º	82.23º	Approximately 15 to 20 minutes after the earthquake, the sea receded, and the usually submerged sand bank Las Delicias could be seen for about 15 minutes. The sea returned with just one very gentle wave and penetrated 100 to 150 m inland crossing the southern tip of the island, which is an extremely flat area. The inhabitants that remained on the island report that the water reached to their knees. The southern portion of the island remained flooded for approximately 20 minutes before the sea receded with great strength back to its original stage. Sea receded 15-20 min after earthquake, remained out for ~ 15 min and returns as gentle wave with 100-150 m run up			Beach
26	Isla Bastimentos	9.35º	82.21º	In the northwest portion of the island, known as Old Bank, the sea receded several meters 10 to 15 minutes after the earthquake. Some submarine vegetation could be seen during this period of time before the sea gently returned 15 minutes later. The sea receded 10-15 min after earthquake and returned gently.			Reef
* Runup heights and coseismic uplifts from Plafker and Ward (1992). Site specific information is provided in Appendix 2 of the Electronic Supplement.