Wednesday, March 28, 2018

Easter week-end at Playa Sosua

The traditional huge crowd will gather at Playa Sosua for the Easter week-end:  extra police on the streets  and volunteers from the Voluntary Civil Guard and Red Cross will be ready to provide assistance to the visitors if needed.  Glassware will be probited on the beach and bars will sell drinks in plastic cups only.  As of writing this wather forecast for the week-end are good:



Come and enjoy Playa Sosua and Happy Easter from PlayaSosua.info!

 

Thursday, March 15, 2018

TSUNAMI RISKS AND TSUNAMI SIMULATION FOR SOSUA AND CABARETE

Yesterday  (March 14 at 9:45) a Tsunami and Earthquake drill took place at Sosua, it was coordinated by the Province of Puerto Plata, the National Government, the National Emercency Comitee and the National Environment Agency: with the sound of sirens public buildings were ecacuated , firefighters and police patrolled the streets.  The Dominican Republic has worked a lot to be ready in case of emergency: there are strict anti seismic rules in its construction laws, real time monitoring  of earthquakes and tsunamis  are in place and emergency protocols and guidelines are in place. 

Earthquake and Tsunami drill March 14, 2018 Sosua

We have decided to contribute to the public authorities' praiseworthy efforts to prevent and manage the earthquakes and tsunami risk by publishing the following study with a risk evaluation and a simulation of what could happen  to Sosua and Cabarete in case of Tsunami.

TSUNAMI RISKS AND TSUNAMI SIMULATION FOR SOSUA AND CABARETE

The island of Hispaniola, which includes Haiti and the Dominican Republic, is a strongly active seismic zone on the boundary of the North American and Caribbean plates which, according to geodetic and gps data, converge at a rate of 2 cm per year on average. Studies carried out using satellite images and measurements with the GPS system (Global Positioning System), found  the internal distribution of displacement of the Caribbean plate (20 ± 2 mm / year) between the fault systems: the Septentrional Fault accumulates displacements of 8 ± 2 mm / year, the Hispaniola Trench of 5± 1 mm / year and the Southern fault system of 8 ± 1 mm / year.  These displacement rates have the potential to accumulate a stress level which could produce, when released, earthquakes of magnitude greater than 6.5.
Observing the USGS map below there are 4 main fault lines causing seismic hazard:

1-The Hispaniola Trench
2-The Septentrional Fault
3-The Enriquillo Fault
4-The Muertos Trough


seismicity map dominican republic
USGD seismicity map: Dominican Republic

In this article we will focus on the Hispaniola trench:  oceanic trenches are topographic depressions of the sea floor, relatively narrow in width, but very long and they form the deepest parts of the ocean floor. Oceanic trenches are a distinctive morphological feature of convergent plate boundaries

The USGS 3D relief underwater map below show the Hispaniola Trench which starts after the Mona Canyon at the end of the Puerto Rico Trench. The Hispaniola Trench, which parallels the north coast of the Dominican Republic and Haiti, and is 550 kilometers (344 miles) long and 4,500 meters (14,764 feet) deep. Scientific studies have concluded that an earthquake occurring along this fault zone could generate a significant tsunami toward the Dominican North Coast.

hispaniola trench
USGD seismicity map: Hispaniola Trench relief map

Deep-sea trenches are susceptible to earthquakes: occasionally, the sudden rupture and movement of the crust can displace thousands of meters of water, setting in motion great tsunami waves. 
Puerto Rico, the U.S. Virgin Islands, and Hispaniola (shared by Haiti and the Dominican Republic) are located near earthquake-prone deep-ocean trenches similar to those that recently have caused earthquakes and a tsunami off Sumatra, Indonesia. A large fault that runs along Sumatra also bears striking resemblance to the Septentrional Fault Zone in Hispaniola. 

Several destructive earthquakes created tsunamis along the fault line of the Puerto Rico Trench and Hispaniola Trench over the last 200 years:  


Histrocial map of Earthquakes which formed Tsunami hitting the  Dominican Republic (Pararas,Carayannis 2010)

Historical map if Tsunamis in the Caribbeans with their run-up measures

A total of 88 tsunamis - most of them moderate - have been reported in the earthquake- prone, volcano-ringed Caribbean area since 1489. Based on the historic record, there is a high probability that a destructive tsunami will be generated again in the Northern Caribbean region that will affect coastal areas of the Virgin Islands, Puerto Rico, the Dominican Republic and Haiti. Tsunami waves with a height of up to 10-12 meters could strike coastal areas. Based on the historical record and rates of crustal movements, large tsunamigenic earthquakes on the Hispaniola Trench can be expected on average every 100 years, but they may occur at more frequent intervals. Thus tsunamigenic earthquake on the northeast coast of the Dominican Republic is highly probable, it is not a question of if another major earthquake will happen but when. The last destructive Tsunami which hit the Dominican Republic was in 1946:


EARTHQUAKE AND TSUNAMI OF 1946

On Sunday, August 4, 1946, a M ¼ 8.1 earthquake struck off the northeastern shore of the Dominican Republic, it caused extensive damage and loss of life. This earthquake also produced a  tsunami  which is thought to have killed 1790 people at Matancitas near Nagua. The Tsunami wave had a run up between 2 and 5 meters with maximum tsunami height of 8 m likely associated with splash up was measured in Playa Boca Nueva (very little information and data ara available from few historical sources). The inundation distance covered by the Tsunami was extensive: inundation distances of 600 meters or more were measured at Las Terrenas and Playa Rincon on the Samana Peninsula. The Tsunami striked the coast just 30 minutes after the earthquake: when the sea receded after the earthquake many went to collect fish from the exposed shore, when the tsunami wave arrived they had no place to run.

 Rare historicla pictures of the 1946 Earthquake and Tsunami, Nagua, Dominican Republic


Until 10 years ago there has not been much concern about thetsunami risk in the caribbeans, this is probaly explained by the comparatively low frequency of the phenomenon, however history and current research confirm the very high tsunami risks to which the Caribbean coasts are exposed. However after the great Tsunamis of Sumatra (2004) and Japan (2011) things changed: in the year 2008, the Seismic Network of Puerto Rico carried out the installation of a tide gauge with the objective of monitoring the level of the sea and its changes, such as the storm surges and Tsunamis, the project involved ONAMET, the Secretary of Environment and the ISU-UASD. This tide gauge is located in Puerto Punta Caucedo and it is part of the 16 tide gauges that will operate in the network of the Caribbean Sea.

Within the National Meteorological Office (ONAMET), a Tsunami Warning Unit has been in existence since September 2008. In 2014 the Dominican Government through the ONAMET put in force a "Manual of Protocol of procedure in case of Tsunamis".
At present, the Tsunami Warning Section maintains a state-of-the-art early warning system. This system consists of 4 tide gauges located in the North, East and South Coast of the territory.
The Tsunami Warning Section is a unit of the Division of Synoptic Meteorology and Forecasts of ONAMET, from where these threats are continuously monitored.

Onamet

TSUNAMI SIMULATION: SOSUA AND CABARETE

Below we will simulate the effect of a destructive earthquake in the Hispaniola Trench off the coast of Puerto Plata under four  different scenarios.

Location of the Earthquake in our simulation

It is important to note that the Hispaniola Trench is just 35 Km off the coast in front of Puerto Plata , such a short distance implies that a tsunami wave generated by the underwater earthquake could reach the coast in just 30 minutes or even less. Readiness and early warning is very important to reduce the damages caused by such an event. We are glad that the communities of Sosua and Cabarete have protocols in place to deal with these risks.
Th Hispaniola Trench rises from a maximum depth of 4500 meters to the the surphace of the sea in just 35 kilometres: this steep shoreline’s slope can result in a resonance that sends more water onshore increasing the Tsunami Run Up when the Tsunami wave reach the coast.

The maximum vertical height onshore above sea level reached by a tsunami is called Run Up.

Hispaniola trench sea bed at -4'500mts  and its  steep slope to the shore line od Sosua and Cabarete


Simulation A: Severe Earthquake and Tsunami

Magnitudo: 8 (similar to the 1946 earthquake and Tsunami of Nagua)
Depth: 30km
Position: Hispaniola Trench 35km north of Puerto Plata Airport
Distance from the shoreline: 35k (21miles)
Tsunami Run Up: 5 meters (similar to the 1946 earthquake and Tsunami of Nagua)

Simulation of inundation caused by a 5mt Run Up Tsunami using a Digital Elevation Model of the Sosua and Cabarete Shoreline

EFFECTS:
-Sosua River valley: 1 km inundation along the Sosua River valley
-POP Airport: partially flooded
-Playa Sosua:  flooded
-El Batey: coastal area  hit and partially flooded
-Los Charramicos:  coastal area partially hit
-Eastern Sosua: coastal area severely hit and partially flooded
-Cabarete: completely flooded


Simulation B: Destructive Earthquake and Tsunami

Magnitudo: 8.5 (stronger of the 1946 earthquake and Tsunami of Nagua)
Depth: 30km
Position: Hispaniola Trench 35km north of Puerto Plata Airport
Distance from the shoreline: 35k (21miles)
Tsunami Run Up: 10 meters stronger of the 1946 earthquake and Tsunami of Nagua)

Simulation of inundation caused by a 10mt Run Up Tsunami using a Digital Elevation Model of the Sosua and Cabarete Shoreline

EFFECTS:
-Sosua River valley: 2km inundation along the Sosua River valley (Sosua Abajo flooded)
-POP Airport: completely flooded
-Playa Sosua: completely flooded
-El Batey: coastal area  flooded
-Los Charramicos:  coastal area severely hit
-Eastern Sosua: partially flooded , coastal area severely hit and completly flooded
-Cabarete: completely flooded




Simulation C: Very Destructive Earthquake and Tsunami

Magnitudo: 9 (similar to the 2004 Sumatra earthquake and Indian Ocean Tsunami)
Depth: 30km
Position: Hispaniola Trench 35km north of Puerto Plata Airport
Distance from the shoreline: 35k (21miles)
Tsunami Run Up: 15 meters (similar to the 2004 Sumatra earthquake and Indian Ocean Tsunami)

Simulation of inundation caused by a 15mt Run Up Tsunami using a Digital Elevation Model of the Sosua and Cabarete Shoreline

EFFECTS:

-Sosua River valley: 2-3km inundation along the Sosua River valley (Sosua Abajo flooded)
-POP Airport: completely flooded
-Playa Sosua: completely flooded
-El Batey: completely  flooded
-Los Charramicos: severely hit and partially flooded
-Eastern Sosua: completely flooded up to  the cabarete-Puerto Plata road
-Cabarete: completely flooded


Simulation D: Very Destructive Earthquake and Tsunami

Magnitudo: 9+ (similar to the 2004 Sumatra earthquake and Indian Ocean Tsunami)
Depth: 30km
Position: Hispaniola Trench 35km north of Puerto Plata Airport
Distance from the shoreline: 35k (21miles)
Tsunami Run Up: 20 meters (similar to the 2004 Sumatra earthquake and Indian Ocean Tsunami)

Simulation of inundation caused by a 20 mt Run Up Tsunami using a Digital Elevation Model of the Sosua and Cabarete Shoreline

EFFECTS:

-POP Airport: completely flooded
-Playa Sosua: completely flooded including the cabarete-Puerto Plata road
-El Batey: completely  flooded
-Los Charramicos: completely flooded
-Eastern Sosua: completely flooded up to  the cabarete-Puerto Plata road
-Cabarete: completely flooded


NOAA Tsunami Animation

We hope that we are lucky enough not to witness such scenarios in our lifetime (and this may well be the case because of the low frequency of such events and because there are costal  areas such as Puerto Rico and Samanà that are much riskier than the Puerto Plata province): we know that the ONAMET is monitoring the tsunami risk in realtime and that the coastal towns will be informed in realtime of such risk and we know that local authorities have emergency planes in places and regular drills are organized to test the local communities' readiness. Education, readiness and informaton will save many lifes if this would ever happen. This is why we prepared this study and simulation, not to generate fear but to help informing the communities of Sosua and Cabarete collaborating with the praiseworthy efforts of the local authorities .

BIBLIOGRAPHY

Análisis de riesgos de desastres y vulnerabilidades en la República Dominicana”,  March 2009 Natalia Gómez de Travesedo, Paola Saenz Ramírez

Es possible que ocurra un sismo catastrofico en Republica Dominicana?",  Hector O’Reilly Pérez

"Tsunami Probability in the Caribbean Region", tom PArsons, Eric Geist

Caribbean Tsunami Warning System” Christa G. von Hillebrandt-Andrade

"Tsunamis in the Caribbean? It's Possible",  Shelley Dawicki, March, 2005

"Assessment of the tsunamigenic potential along the Northern Caribbean Margin", George Pararas-Carayannis, 2010

"Coulomb stress evolution in Northeastern Caribbean over the past 250 years due to coseismic, postseismic and interseismic deformation",  Ali Syed Tabrez  Andrew M. Freed  Eric Calais  David M. Manaker  William R. McCann, 2008

"Historical perspective on seismic hazard to Hispaniola and the northeast Caribbean region", Uri S. ten Brink,William H. Bakun, and Claudia H. Flores 2011



Thursday, March 8, 2018

Playa Sosua 1910-2018

The new beach formed by the abnormal waves of March 5 and March 6, 2018 where once stood the pier...

Playa Sosua

Tuesday, March 6, 2018

Storm waves at Playa Sosua

On Monday and Tuesday (March 5 and March 6) massive waves hit the North Coast of the Dominican Republic:  Sosua, Puerto Plata and Cabarete were not spared....

This picture of Puerto Plata Airport posted by Jean Suriel on Twitter became viral...massive waves flooding the airport of Puerto Plata.

The storm was caused by cold wind and low pressure from the North Atlantic Ocean:

North Winds caused by the low pressure area in the North Atlantic are hitting the  DR North Coast

The COE (Centro de Operaciones de Emergencia) has prohibited swimming in the beaches of Sosua, Cabarete , Boca de Yascica because of the danger caused by abnormal waves.

The waves hitting Playa Sosua has moved a lot of sand from the Weast end of the beach to its East end: Playa Sosua West has lost a lot of sand and the rocks are now exposed while a new beach formed on Playa Sosua East in front of Hotel Bellamar and Hotel Victorian House. This is likely to be a temporary phenomenon, normal currents should reshape the beach in the coming weeks.

Playa Sosua: sand movements 

The new beach forming East of Playa Sosua (photo by Rissatory Arte)


Damages and erosion West of Playa Sosua



Be prudent and stay safe for the next couple of days: no swimming still in force.