Peligros de Tsunami en Puerto Rico

Peligros de Tsunami en Puerto Rico
Alberto M. López Venegas
Departamento de Geología | PRSN
Taller de Desalojo Vertical
Colegio de Ingenieros y Agrimensores
18 de junio de 2012
Agenda:
1.
Introducción
2.
Placas Tectónicas
3.
Mecanismos de Generación de Tsunamis
4.
Tsunamis en Puerto Rico y vecindad
5.
•
1 de noviembre de 1755
•
4 de noviembre de 1867
•
11 de octubre de 1918
•
4 de agosto de 1946
Potencial de Tsunamis en Puerto Rico
Chile
1960
Alaska
1964
Sumatra
2004
Agenda:
1.
Introducción
2.
Placas Tectónicas
3.
Mecanismos de Generación de Tsunamis
4.
Tsunamis en Puerto Rico y vecindad
5.
•
1 de noviembre de 1755
•
4 de noviembre de 1867
•
11 de octubre de 1918
•
4 de agosto de 1946
Potencial de Tsunamis en Puerto Rico
¿Qué son las placas tectónicas?
Es el término utilizado para explicar una serie de divisiones sistemáticas que
ocurren en la corteza terrestre y cuyas interacciones resultan en los
procesos dinámicos del planeta.
Una mejor visualización de este concepto:
• Una superficie plana adaptada a una esférica
• La cáscara de una naranja
• Botes apiñados uno al lado del otro
Placas “flotan” sobre un “líquido” más
denso: el Manto.
Estructura del Planeta
Debido a que la litósfera es de característica quebradiza, se rompe en pedazos para
acomodar la curvatura del planeta. Estos pedazos forman las placas.
Conocimiento actual (cont.)
La interacción entre placas ocurre de forma sistemática.
Aunque las cualidades difieren de lugar en lugar, el
mecanismo es siempre el mismo, lo cual da paso al balance
del planeta.
Agenda:
1.
Introducción
2.
Placas Tectónicas
3.
Mecanismos de Generación de Tsunamis
4.
Tsunamis en Puerto Rico y vecindad
5.
•
1 de noviembre de 1755
•
4 de noviembre de 1867
•
11 de octubre de 1918
•
4 de agosto de 1946
Potencial de Tsunamis en Puerto Rico
Fuentes de generación de tsunamis
Tsunamis pueden ser causados por procesos sísmicos y
no sísmicos:
1. Dislocación del suelo marino (falla): como consecuencia
de un terremoto
2. Deslizamiento: movimiento pendiente abajo de material
por influencia directa de la gravedad
3. Erupciones volcánicas: material expulsado
violentamente a grandes velocidades
4. Impacto de meteoritos: cuerpo celeste foráneo al planeta
impacta la superficie en presencia de líquido.
Tsunamis entre 1790 y 1990
Fuentes Sísmicas Globales
La Ciencia de los Tsunamis - Parte II:
Generación
Causante: Movimiento de placas
Zonas convergentes (subducción): lugares donde
se generan los tsunamis mas grandes
Fuentes más comunes de tsunamis
Antes del terremoto (inter-sísmico)
Sísmicas: Terremotos
 Megaterremotos (Mw ~ 9) –
también conocidos como
“Terremotos Tsunamigénicos”
 “Terremotos Tsunami” o terremotos
lentos deficientes en energía de
alta frecuencia.
Durante el terremoto (co-sísmico)
Después del terremoto (post-sísmico)
Credit: ga.gov.au
Fuentes más comunes de tsunamis
Sísmicas: Terremotos
Fuentes más comunes de tsunamis
Deslizamientos:
Ya sean submarinos o
superficiales. Dejan evidencia
clave de su ocurrencia;
escarpados notables y pie (base)
del deslizamiento. El tamaño del
tsunami puede ser estimado
fácilmente por la calculación del
volumen desplazado en sus
zonas de excavación y
deposición.
Fuentes más
comunes de tsunamis
Velocidad de la masa tiene que ser lo
suficientemente rápida para que
provoque un cambio en la columna de
agua.
Esto indica cúan abrupto tiene que ser el
deslizamiento.
El tamaño del tsunami es directamente
proporcional al volumen del
deslizamiento, aunque no todo
contribuye
Geometría, distancia y localización del
deslizamiento producirá la polaridad de
la primera ola a tierra.
1929 Grand Banks
After the tsunami, ca. November 1929
The 1929 tsunami caused about $1
million in property damage on
Newfoundland Burin Peninsula. Giant
waves crushed buildings, swept
houses and boats out to sea, and
destroyed wharves, flakes, and other
structures.
Storegga Slide, Norway : 8200 yrs ago
This landslide generated a huge tsunami with waves of up to 15 m that destroyed Stone Age
communities in Western Norway.
Evidence of the tsunami on-land have been observed in both Scotland and the Faroe islands.
This area is known for large oil and natural gas reservoirs. Therefore, a landslide of this
magnitude today would be catastrophic to pipeline systems and underwater production facilities
on the sea floor.
3D image of massive Storegga slide
Approximately 3,500 km3 of material might have been displaced–
http://www.ngi.no/en/Contentboxes-and-structures/Reference-Projects/Reference-projects/Ormen-Lange-and-Storegga/
Papua New Guinea July 17, 1998
Village of Arop
was totally
vanished.
Noitice tsunami
scours crossing
the sand spit.
Photo credit: National Mapping
Bureau of Papua New Guinea.)
Tsunami overtopped the sand spit (avg
width = 100 m, max elev= 3 m)
Village debris can be seen on the lagoon
behind the sand spit.
Tsunami
penetration
(inundation) was
computed at 0.5
km in-land.
Agenda:
1.
Introducción
2.
Placas Tectónicas
3.
Mecanismos de Generación de Tsunamis
4.
Tsunamis en Puerto Rico y vecindad
5.
•
1 de noviembre de 1755
•
4 de noviembre de 1867
•
11 de octubre de 1918
•
4 de agosto de 1946
Potencial de Tsunamis en Puerto Rico
Los tsunamis más catastróficos y
documentados en el noreste caribeño:
– 1 de noviembre de 1755: Lisboa, Portugal (Mw=8.7)
– 18 de noviembre de 1867: Paso de Anegada (Ms=7.5)
– 11 de octubre de 1918: Paso de la Mona (Mw=7.2)
– 4 de agosto de 1946: República Dominicana (Mw=8.0)
Se han documentado 53 tsunamis en el área del Caribe desde
que los colonizadores llegaron en 14981.
1 O’Loughlin y Lander (2003)
Northern Caribbean Plate Boundary
Zone
~250 km wide x ~2,000 km long
- Microplates accommodating stresses between NA and CA
Gonave microplate
(Heubeck et al. 1998;
Mann et al. 1991)
Hispaniola platelet
(Byrne et al. 1985)
PR-VI microplate
(Masson and Scanlon
1998;
Jansma et al. 1991)
Rupture zones of earthquakes in NCPBZ:
Dolan and Wald (1998)
The 1755 Lisbon Earthquake

The strongest earthquake recorded in Europe, Ms ~8.7

Uncertainties regarding epicenter location and focal mechanisms

Effects in Europe:

Tsunami runup of 6 m at Lisbon and as high as 15 m at Cape
S. Vincente (SW Portugal)


250 m inland inundation in Lisbon

Up to 100,000 casualties from earthquake + tsunami

Wide spread effects felt from Morocco to Cornwall (S. UK)
Effects in the Caribbean and the US East Coast:

7 m runup at Saba-Netherlands Antilles

4.5 m runup at St. Martin

Reports of flooding in Santiago de Cuba

Reports of casualties in Brazil

Damage to boats in Newfoundland, Canada

No reports in the US East Coast
Best-fitting models of 1755 Lisbon epicenter:
Epicenter in Horseshoe plain south of Gorringe Bank
Strike orientation of 345°, possible reactivation of
the Paleo-Iberia African Boundary
Tsunami Hazards to the US East Coast:
Highly dependent on topography and strike
orientation
Florida would be subjected to greater hazard for EQ
sources east of the Madeira Ridge
Damages would be greater in range from EQ
sources west of the Madeira Ridge
Anegada Passage - November 18, 1867
U.S. to purchase the Danish West Indies, hence
several Navy ships were at the time of the treaty
and documented well the event.
Two earthquakes ten minutes apart at ~14:40
local
Ms≈7.5 originating on the Anegada Passage
between St. Thomas and St. Croix
Approximately 481 aftershocks until December 11
First wave arrived at St. Thomas ~5 or 15 minutes
after mainshocks
Leading depression observed at the Virgin islands
(both sides of the Anegada Passage),
southeastern coast of Puerto Rico and Lesser
Antilles islands.
Tsunami reached the Venezuelan coast in
approximately 60 minutes.
USS Monongahela
Maximum run-up in meters at various locations where the tsunami was observed:
November 18, 1867
Zahibo et al. (2003a)
Maximum run-up in meters at various locations where the tsunami was observed:
Four fault scenarios (S1-S4)
120 km length x 30 km wide
70° dip and 90° slip
S1=0°, S2=15°, S3=20°, S4=25°
Center of fault at 18°N 65°W
MW =7.9 (M0=8.6x1027 dyne-cm)
November 18, 1867
Zahibo et al. (2003a)
St. Thomas
St. Croix
November 18, 1867
St. Thomas
St. Croix
November 18, 1867
St. Thomas
St. Croix
November 18, 1867
Line 18
November 18, 1867
Although seismic reflection data is not
particularly conclusive of a transtensional
fault, preliminary results of tsunami modeling
transtensional?
on the ESE-oriented 110 km fault length
show good agreement, both in arrival times
and run-up at various locations.
Stay tuned for these results!
Line 23
November 18, 1867
Barkan & ten Brink, 2010
Barkan & ten Brink (2010)
Used high-resolution bathymetry
from the PRVI region
Made tsunami simulations using
the on-line tsunami simulation
program COMCOT
Based on bathymetry two
potential faults oriented 100 and
120 degrees were used to
generate simulations
Simulations based on Zahibo’s
work (strike from 60-90 degrees)
showed high residuals when
compared to the two faults
modeled in their study
Predicted arrivals were
depression waves in agreement
with observations
Mona Passage:
October 11, 1918
Overview:
On Friday, October 11, 1918 at 10:14 am local time,
Puerto Rico experienced an (ML 7.5 Gutenberg &
Richter, [1954], MW 7.2 Doser et al. [2005]) earthquake
originating in the Mona Passage between Puerto Rico
and the Dominican Republic.
Seismic waves were followed by a tsunami that affected
first the northwest coast of Puerto Rico and
progressively south along the coast.
Approximately 110 lives were lost due to the earthquake
and the tsunami, with approximately $4 M estimated in
damages.
Tectonic or landslide? Exact cause of the tsunami was
unclear.
Repeat of such an event today would be catastrophic
and damages estimated in the tens of millions.
Field survey documented tsunami observations
at seven locations in western Puerto Rico.
Modelando la fuente por mecanísmo de fallamiento
Primer intento en recrear los valores de la ola en los
lugares visitados por Reid y Taber en 1918.
Mercado y McCann (1999)
Nuevas tecnologías permiten realizar estudios que antes eran imposibles hacer. Este es el
caso de sondas para estimar profundidad del lecho marino (batimetría).
El Servicio Geológico de los Estados Unidos (USGS) ha llevado a cabo varias campañas para
crear un mapa del suelo marino de alta resolución. Este nuevo recurso provee los datos
necesarios para inspeccionar e identificar posibles fuentes del maremoto.
Una vez identificada la fuente, se llevan a cabo campañas de estudios sísmicos marinos para
confirmar la fuente, cuyas dimensiones se utilizan como modelo inicial para simulaciones.
Escarpes de un deslizamiento bastante fresco se pudieron observar muy claramente con la
batimetría de alta resolución. La cabecera de este escarpado se encuentra al norte de la
cordillera submarina de Desecheo. El área estimada es de 76 km2
Evidencia de un
Deslizamiento
Submarino
Area de excavación del
deslizamiento es de 9 km
de ancho por 9 km de
largo
Volumen de material
removido asciende a los
10 km cúbicos basado en
un diferencial vertical de
150 metros en los
escarpados
La ubicación del
deslizamiento produce
tiempos de arribos en
acorde con los datos
observados.
Líneas sísmicas utilizadas para demostrar
el escarpado del deslizamiento.
Esto indica como la plataforma de
carbonatos falló internamente.
Northwest
Desecheo
Ridge
Line 56

USGS cruise in October 2006
aboard R/V Pelican
Seismic line 61 (East to West)
shows landslide scarps
Line 61
Estimated slide thickness at this location is ~ 150
meters.
Using landslide area, we computed displaced volume
of ~10 km3.
Line 56
Head scarp
Multiples
Desecheo
Ridge
Northwest

Seismic line 56 (NW
to SE) shows
landslide headscarp
and show carbonate
platform failed
internally, probably
along a weaker
interface.
Reid and Taber (1919)
Descripción de los daños causados a los cables del
Telégrafo. Cable francés de St. Thomas a Puerto Plata
Comandante Morrell (CS Henry Holmes) describiendo
Los daños al cable Kingston-San Juan:
Y lo mismo ocurrió luego de la réplica del 24 de octubre:
Sección transversal del
diámetro del cable
Kingston-San Juan:
Variacion de costa (izq.) a
una profundidad > 1300
m. Escarpe del
deslizamiento es a los
1200 m.
Fuente: Bill Burns http://www.atlantic-cable.com
Tsunami Modeling:
-NOAA Puerto Rico bathymetry grid
-Grid dimensions: 134 x 157 km
-Rotated grid 10 degrees clockwise
COULWAVE tsunami package
Model produces excavation
area, volume and thickness
in agreement with
bathymetry
(Lynett and Liu, 2002)
-Model rotational slides with userspecified slide duration.
-Employs linear and non-linear
terms.
-Computes free-surface as the
landslide progresses.
Preliminary results obtained using COULWAVE tsunami modeling package (Lynett & Liu, 2002)
N
Parameters used:
-Landslide dimensions: 10 km x 8 km
-Change in depth due to slide: 20 m
-Duration: 200 sec
-Grid resolution: 200 m
-Friction coeff: 0.003
Preliminary results obtained using COULWAVE tsunami modeling package (Lynett & Liu, 2002)
N
Parameters used:
-Landslide dimensions: 10 km x 8 km
-Change in depth due to slide: 20 m
-Duration: 200 sec
-Grid resolution: 200 m
-Friction coeff: 0.003
-Known variables: landslide area, location and thickness.
-Unknown variables: landslide duration and bottom friction coefficient.
-c2 test was used to obtain these unknown variables by comparing Reid & Taber (1919) flow
depth observations with simulations using a coarse grid of 1600 meters.
-27 m/sec landslide velocity
ML =8.1 (Gutenberg & Richter, 1954)
DR- August 4, 1946
Questionable casualties: Is it really close to 1,800? Lynch & Bodle (1949) initially
reported around 100, and mostly due to the tsunami annihilating the village of Matancitas,
a small coastal town in northeastern Dominican Republic.
Debate over causative fault
No seismic moment was computed and cause of tsunami was left unresolved.
Hence, if good quality paper records of seismograms were available, then the procedures of
Okal and Talandier (1989) to compute the variable period Mantle magnitude (MM) and Newman
& Okal (1998) to compute estimated energy were applicable to determine whether earthquake
was slow and capable of generating the tsunami.
EE=3.10 X 1022 ergs
M0=5 x 1027 dyn-cm
Slow earthquakes (Vr in
the order of ~1km/sec)
Θ < -5.62
Hispaniola event shows
Θ = -5.2, which plots in the
mainstream population of
earthquakes. Hence not
a ‘tsunami’ nor a tsunamigenic
earthquake.
So, is it really a landslide?
Dolan and Wald (1998)
Maximum amplitude waves for
each of the three cases:
2 focal mechanisms:
-55 cm displacement
-Fault: 200 x 100 km
-M0 = 5 x 1027 dyn-cm
Russo and Villaseñor (1995)
Landslide (asymmetric dipole)
Landslide:
-30 m trough
-30 x 30 km landslide base
Maximum amplitudes
observed by earthquakes, and
from these DW98 is more
efficient.
Landslide is more localized
No apparent landslide seen on the available
high-resolution bathymetry (>1000m).
Does this means that the landslide is shallower
than 1km depth or that it is further north?
Agenda:
1.
Introducción
2.
Placas Tectónicas
3.
Mecanismos de Generación de Tsunamis
4.
Tsunamis en Puerto Rico y vecindad
5.
•
1 de noviembre de 1755
•
4 de noviembre de 1867
•
11 de octubre de 1918
•
4 de agosto de 1946
Potencial de Tsunamis en Puerto Rico
Northern Caribbean Plate Boundary
Zone
~250 km wide x ~2,000 km long
- Microplates accommodating stresses between NA and CA
PRVI microplate (Jansma et al., 2000) has been defined as a block in northeastern
Caribbean within the NCPBZ that has the following boundaries: Puerto Rico Trench
(north), Muertos Trough (south), Anegada Passage (east), and Mona Passage (west).
Compression is observed on both north and south while extension east and west.
Earthquakes along these features are capable of generating tsunamis.
Earthquake density based on 20 years of seismic recording in the region (1986-2006) by
the Puerto Rico Seismic Network.
Seismic zones have been defined and correlate with the location of identified faults onshore and off-shore Puerto Rico – Virgin Islands.
Offshore features dominate, and with northern area accommodating the majority of
displacement, while in southwest Puerto Rico is the dominant feature on-land.
Most active seismicity occurs in southwest PR along a
left-lateral strike-slip fault oriented NW-SE
A study by ten Brink & Lin (2004)
using Coulomb 3.0 suggests that
no major event may occur along
the PR Trench. This study is
based on the occurrence of leftlateral strike-slip faults near the
trench that may accommodate
the motion between the plates.
A different story arises on the
west, where Hispaniola is pinned
with the Bahamas platform and
thus creates high coupling along
the Northern Hispaniola
deformed belt, and the
Septentrional fault.
Along the south, the Muertos
trough has been recently
reconsidered (Granja-Bruña et
al., 2010) as a back-arc thrust
and not a subduction zone,
therefore having less seismic
hazard as previously thought.
Another work that support this idea is the recently published work by ten Brink & López (GRL,
v.39, 2012) in which continuously operated GPS sites in the Puerto Rico – Virgin Islands region
are modeled with Coulomb 3.0 with 4 discrete patches along the NA-CA interface. The study
suggests the PR Trench is actually in extension and is improbable to cause a large events.
However, this does not mean minor events can occur at the trench nor larger events along the
north or southern slope of the trench. Moreover, any event can cause a disturbance along
weak and fragile layers of the carbonate platform.
Batimetría de alta resolución está disponible hoy día para visualizar que tipo de
características ofrece el suelo marino en esa localidad. Si el tsunami lo generó
una falla o un deslizamiento, entonces la evidencia en el suelo marino debe de ser
reflejada en la batimetría.
High-resolution bathymetry from the USGS is used to identify past submarine landslides and
potential slides based on potential faults on nearby slides.
Loiza amphitheater
Arecibo amphitheater
Ten Brink et. al, 2007
ten Brink et. al, 2007
50 km across
1147 km2
910-1500 km3
35 km across
692 km2
ten Brink et. al, 2007
Grindlay et al. (1998) analyzed seismic line 20 from a cruise in 1996 on-board the R/V M. Ewing
Estimated 57 km across with head scarp at 3000 -3500 m depth with a potential landslide volume
of 900-1500 km3. Great uncertainty exist on the age of the slide and the history (progressive?)
Submarine Landslide Tsunami Simulations
Horrillo et al. (2010)
(Horrillo
2010)
Horrilloet.
et al.,
al. (2010)
Tsunami simulation of entire Arecibo amphitheater submarine landslide using COULWAVE
(Lynette & Liu, 2002) for simulating a rotating landslide.
Mercado et al. (2002)
Future submarine landslides along weak and
northly-dipping carbonate platform that is
susceptible to debris avalanches
Latest tsunami modeling employing
the methods of Kovalik et al. (2006)
and following procedures of Horrillo
et al. (2010).
As a validation exercise the October
11, 1918 scenario is updated with
better resolution and employing the
VOF3D method of TSUNAMI3D.
Using the highresolution
bathymetery up
to 18 possible
scenarios of
submarine
landslides along
the coastal
areas around
Puerto Rico
have identified.
Inundation and
run-up values
from this
simulations are
on-going.
5 posibles segmentos de ruptura:
Lesser Antilles and Southern
Caribbean maximum amplitudes:
-40 cm displacement
-200 x 100 km fault
-M0 = 4 x 1027 dyn-cm
Northern Lesser Antilles:
immediate effect on islands and
waves reaching 50 cm
Southern Lesser Antilles
immediate effect on Barbados
and southern LA islands
reaching waves of up to 50 cm
Southern Caribbean Deformed
belt
Venezuela and all across the
Caribbean sea to PRVI
Southern Caribbean sources
Source at Southern Caribbean Deformed Belt at
northern Venezuelan coast. Historical records report
an event in this location in 1530 that resulted in waves
of up to 7.3 meters in height in the near field.