kick em jenny forvenezuela[1]

8/4/2019 Kick Em Jenny ForVenezuela[1]

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Seismic Research UnitThe University of the West IndiesSt. AugustineTrinidad

Tel 868 662 4659 Fax 868 663 9293 e-mail [email protected]

Marine and Coastal Hazardsfrom Kick em Jenny

submarine volcano, southernGrenadine Islands

John B. ShepherdSeismic Research Unit

The University of the West IndiesSt. Augustine

Trinidad

Presentation to meeting of Venezuelan and associatedseismologists, FUNVISIS, June 2000


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We are strengthening the monitoringsystem in order to be prepared for

any renewal of activity2000 June 10

Kick em Jenny is NOT erupting

There are NO signs of unusual activity

The most recent eruption was in 1990

We expect future eruptions butno eruption is imminent right

now


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Where is Kick em Jenny?

First accurate survey from HMS Hecla in 1972 located the summit of thevolcano at 12.30 degrees North, 61.63 degrees West

First report on July 24 1939 said 5 miles distant from Sauteurs bearing 12 - 15degrees magnetic from the Gunton Estate House


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More detailed location - from 1972 survey


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Date Phenomena1939 July 24 Subaerial euption

Local earthquakes felt strongly

Two eruption columns to 270 m above sea level

Tsunami 1 meter in open water

1943 October 10 Submarine eruption.

T phase recorded in Martinique.

1953 October 30 Submarine eruption

T-phase recorded, Trinidad to Puerto Rico

Earthquakes felt Grenada

1965 October 30 Submarine eruption

T -phase recorded from Trinidad to Puerto Rico

Minor tsunami

1966 May 5 Submarine eruption.

T-phase throughout region continue to May 07

1966 August 3 Submarine eruption

168 earthquakes recorded

Felt strongly, Grenada

T-phase throughout region

1972 May 7 Submarine eruption for 5 hours

T-phase

1974 June 9 Subaerial eruption.

Started 0600 GMT.

Sea boiling turbulently and spouting steam

T-phase

1977 November 11 Submarine eruption

T-phase

1988 December 29 Submarine eruptionFelt and heard in Grenada and Martinique

T-Phase

1990 March 26 Subaerial eruption

Water discolured and turbulent

Felt strongle Grenada

T-Phase

Known Eruptions since 1939


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Depth to summitDate Ship Depth

1962 October HMS Vidal 232m

1966 June HMS Lynx 192 meters

1972 May HMS Hecla 190 meters

1976 May RV Gillis 190 meters

1978 April RV Endeavor 160 meters

1981 October N.O. Noroit 160 meters

1985 April RV Conrad 160 meters

1989 April Submersible 150 meters

1997 May RV Malcolm Baldridge 177 meters*


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What are the hazards of Kick em Jenny?

The most significant indirect hazard is that a sea wave or tsunami could begenerated by eruptions of Kick em Jenny. The 1939 eruption generated strong

waves in Sauteurs. These waves were noticed as far away as Barbados. A major

tsunami conceivably could affect the whole of the eastern Caribbean region asfar south as Venezuela and as far north as the Virgin Islands. For this reason wehave studied the possibility of tsunami generation by Kick em Jenny very

carefully. First some facts about tsunamis in general.

1 Direct Hazards.

Other eruptions 1974 June 9 and 1990 March 26 also broke the surface ofthe sea. An eruption of this sort off the coast of Japan in 1952 sank a 500-tonne research vessel with all hands

The July 24 1939 explosions at Kickem Jenny propelled solid rocks ofconsiderable size to a height of 900 feet above the surface of the sea. Any

boats or ships within a radius of one kilometer or more of the volcano were atimmediate risk. This situation could happen again at any time although webelieve that there would be 12 - 24 hours warning at least.

Eventually the volcano will break the surface to form a new island. It willthen present the full range of hazards to neighbouring islands. Fortunately theprevailing winds are from east to west at low level so most ash would becarried out into the Caribbean. The le de Ronde and nearby islands andpossibly Sauteurs are within range of ballistic fragments

2 Indirect hazards


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Seismic Research UnitThe University of the West Indies

St. AugustineTrinidad


The maximum height above sea level reached by a tsunami is called therunup. The

area flooded is the inundation. Both of these quantities depend on near-shore

bathymetry and topographyso that both run up and inundation may vary rapidly

along the shore line.

The word tsunami comes from two Japanese words which taken together mean

harbour wave

The word was chosen to avoid the older term tidal wave. Tsunamis have no

connection with the tides

True tsunamis consist of a series of waves, not a single pulse An essential feature that the

wavelength - that is the distance between successive crests - is much longer than the deptof the ocean.

Tsunamis travel with a velocity which depends on the ocean depth. The deeper the ocean

the faster they travel

In the deep oceans the velocity is about 800 km/hr (500 miles/hr). This is about the

speed with which a jet airliner travels.

Far out at sea the height of the wave is only a meter or two, even for the biggest

tsunamis.

As they approach land, they feel the bottom of the sea which slows them down. At the

same time, the height of the wave increases. A one-meter tsunami at sea may become a

thirty-meter tsunami as it approaches land.

Not all tsunamis break as they approach land. Only about one in five looks like the

picture at the top of this slide. Often the first sign is a withdrawal of the sea. It then

returns like a rapidly-rising tide. This may be repeated several times as successive

crests arrive.


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Some terminology

Wavelength. This is the distance from one crest of the tsunami to the next. For genuine tsunamisthe wavelength in deep water is very much greater than the depth of the ocean. The mean depth ofthe ocean is about 5 km so that the wavelength of typical tsunamis is greater than 50 km. At 800km/hr there is at least 4 minutes - usually longer - between the arrival of one crest and the arrival ofthe next one

Velocity - Far from land tsunamis travel at about 800 km/hour (500 miles/hour). They slowdown considerably as they approach land

Runup - far from land the amplitude of a tsunami may be only a few meters. As itapproaches land the amplitude increases rapidly. The maximum height reached is called the

runup

Inundation. This is the maximum distance inland from the normal coastline reachedby the tsunami or alternatively the maximum area covered by water as a result of thetsunami

Seismic Research UnitThe University of the West Indies

St. AugustineTrinidad



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Causes of tsunamisA: Earthquakes

Tsunamis are generated only by shallow earthquakes (depth less than 50 km)

Not all big earthquakes generate tsunamis.

B Volcanic activity

a Earthquakes accompanying eruptions

b Pyroclastic flows impacting on water

c Submarine explosions

d Caldera collapse or subsidence

e Avalanches of cold rock

f Base surges with accompanying shock waves

g Avalanches of hot material

h Air waves from explosions

i Lahars (mudflows) impacting on water

j Lava avalanching into sea

C Landslides into the sea.

D Impact of objects into the sea

Asteroids Comets meteorites

All earthquakes beneath or close to the sea disturb the sea surface, but not all of

these disturbances are tsunamis. True tsunamis are generated only by earthquakes

of magnitude greater than about 6.5


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Potentially tsunamigenic

earthquakes

Of these 40 earthquakes only two are KNOWN to have generated significant tsunamis. Twoothers generated very local, small-scale tsunamis.

The diagram shows the locations of all earthquakes in the eastern Caribbean since the Europeansettlement in about 1500 AD which were potentially tsunamigenic. By this is meant that they

were of sufficiently high magnitude ( > 6.5) and sufficiently shallow depth (< 50 km). There areapproximately 40 earthquakes in just under 500 years which satisfy these criteria.


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Potential Tsunami sources 2

Volcanoes


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Spurious and exaggerated

Caribbean tsunamis

These land slides generated separate sea waves which some authors havemistaken for a single tsunami

Jamaica June 7 1692 - The Port Royal Earthquake

Often quoted as an example of tsunami damage

In fact the main damage at Port Royal was caused by collapse of unstable land

The earthquake generated numerous landslides, some on sea floor many into sea


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Ray paths near Kick em Jenny


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More distant ray paths


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Travel times - close by


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Travel times - Grenadines


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Travel times - Eastern

Caribbean


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Predicted amplitudes (m) at

selected locationsLocation Worst Case High probability Medium Probability

Ile de Ronde 10 (38) 1 (4) 5 (15)Carriacou 8.76 (19.4) 0.93 (2) 3.45(7.63)

Northern Grenada 7 (29) 0.9 (3) 4 (11)

Union Island 7.58 (16) 0.81 (1.7) 3 (6.28)

Bequia 5.6(15) 0.59 (1.6) 2.2 (5.85)

Kingstown 4.54 (12) 0.5 (1.3) 1.8 (4.7)

Trinidad (Maracas Bay) 4.24 (14) 0.45 (1.5) 1.67 (5.6)

Trinidad (Port-of-Spain) 1.55 (7) 0.16 (0.73) 0.61 (2.7)

Margarita 1.97 (10.77) 0.21 (1.15) 0.78 (4.24)

Blanquilla 1.15 (4.16) 0.12 (0.44) 0.45 (1.64)

Paria Peninsula 2.18 (16.31) 0.46 (1.73) 1.71 (6.42)

The current depth of Kick em Jenny summit is too great to permit immediateexplosive eruptions. Some effusive growth is required before the volcano moves back

into the explosive range of depths.

High probability case corresponds to the 1939 eruption. Actual predicted amplitudeswere observed at Ile de Ronde, northern Grenada (Sauteurs) and Barbados. In otherlocations the waves may not have been recognized as tsunami waves. Waves of thisamplitude can be considered to be certain within the next few decades.

Worst case scenario corresponds to the biggest eruption of this type of which Kick

em Jenny is capable. Such an eruption is most unlikely.

We recommend adoption of the medium probability scenario for planning. Theprobability of this scenario is about the same as that of a category 5 hurricane hittingTrinidad head on.


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Planning for tsunamis

5 and 7 and 8 are the main aims of our project

1 For most earthquake-generated tsunamis in the Caribbean distances traveled are mainlyless than 200 km

2 This means that the time between earthquake occurrence and arrival of thetsunami is less than 30 minutes, and may be only one or two minute

3 Since earthquakes cannot be predicted, tsunamis cannot be predicted.

4 If there had been a tsunami-warning system in operation in the Caribbean forthe past 500 years it would have issued a warning only once (1867) for

earthquake-generated tsunamis.

5 The best preparation for earthquake-generated tsunamis is therefore

Public education about effects of tsunamis

Mapping of areas subject to tsunami inundation

6 Eruptions of Kick em Jenny CAN be predicted. The volcano needs time tobuild up to full eruption (at least 24 hours in 1939).

7 Therefore we can predict volcano-generated tsunamis by monitoring the volcano.

8 We can also map areas subject to tsunami inundation as for earthquake-generated events.


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Proposed Monitoring network


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Acoustic picture of Kick em Jenny taken in

1997


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