FAULTS LAN

D

BOTTOM OF THE

SEA

DECEMBER 26, 2004THE INDIAN OCEAN TSUNAMI CLAIMED

OVER 250,000 LIVES ACROSS 14 COUNTRIES

On March 11, 2011 Japan was hit by 9.0 magnitude earthquake and

it was followed by tsunami.

Figure 2. Source characteristics of the March 11 earthquake. Left: March 11 epicenter and rupture area. Also shown is the aftershock region and the source areas of previous historical earthquake (adapted from Kanamori, 2011). Right: simplified cartoon of the rupture sequence and tsunami generation. Yellow zone shows the initial rupture downdip of the epicenter (2). After about 75 seconds, the rupture migrated updip of the epicenter (pink zone). The second phase of rupture propagated slowly and produced very large slip (3).

Figure 12. Approximate inundation area in the west area of Higashimatsushi-ma City. This region was particularly vulnerable because the tsunami attacked from several directions. The star marks the location of the evacuation building shown in Figure 13. Note its proximity to higher ground on the hillside.

Figure 15. Approximate inundation area in Sendai, Natori, and Iwanuma Cities. Pins mark the locations of Wakabayashi, Yuriage, and the Sendai Airport, discussed in the text. The tsunami deposits transect is close to the black arrow where the tsunami penetrated about 5 km.

Tsunami is a series of water waves caused by the

displacement of a large volume of a body of water,

usually an ocean.

What is a tsunami?

• A tsunami is a series of waves created when water is moved very quickly. Underwater earthquakes are the most common causes of tsunamis, but underwater volcanic activity can also trigger a displacement in the water, and create a mega-wave.

HOW DOES A TSUNAMI IS FORMED?

HOW DOES A TSUNAMI IS FORMED?

TSUNAMI IS FORMED WHEN THERE IS A SUDDEN UPWARD MOVEMENT OF ROCKS ALONG A FAULT AT THE

SEAFLOOR.

Causes of Tsunami

Causes of Tsunami……..

Meteorite impacts

Size of Tsunami

Tsunamis have an extremely long wavelength (wavelength is the

distance between the crest (top) of one wave and the crest of the next

wave) -- up to several hundred miles long. The period (the time between two successive waves) is also very long -- about an hour in deep water.

In the deep sea, a tsunami's height can be only about 1 m (3 feet) tall. Tsunamis are often barely visible when they are in the deep sea. This makes tsunami detection in the deep sea very difficult.

A tsunami can travel at well over 970 kph (600 mph) in the open ocean - as fast as a jet flies. It can take only a few hours for a tsunami to travel across an entire ocean. A regular wave travels at

up to about 90 km/hr.

REGULAR SEA WAVE AND TSUNAMI WAVE

• Tsunami wave is so powerful because it involves the whole depth of ocean while surface waves are just sea-surface wave generated by wind.

Why does a tsunami rise to such great height when it reaches the shore?

As tsunami waves reaches the shore it slows down but the tail ends keep on

coming at a great speed. So the water piles up and grows to dangerous

heights, destroying everything in its path.

IS TIDAL WAVE AND TSUNAMI WAVE SIMILAR?

Tsunami should NOT be known as tidal waves. Tsunamis are sometimes incorrectly

called "tidal waves" -- tsunamis are not caused by the tides (tides are caused by

the gravitational force of the moon on the sea).

Can you identify the relationship of earthquake and tsunami?

Does all fault movement under the sea will result to tsunami?

NO.WHY?If the fault movement is horizontal (sideways), the water above will not be disturbed.The movement has to be in VERTICAL DIRECTION (UPWARD OR DOWNWARD).

Most tsunamis, about 80 percent, happen within the Pacific Ocean’s “Ring of Fire,” a geologically active area where tectonic shifts make volcanoes and earthquakes common.

You are near the beach when you suddenly feel an earthquake. What will you do?

You need to run to the highest place that you can find.

WARNING SIGNS!

An earthquake is a natural tsunami warning.

If you see the ocean receding unusually rapidly or far it's a good sign that

a big wave is on its way. Go to high ground immediately.

Experts believe that a receding ocean may give people as much as five

minutes' warning to evacuate the area.Remember that a tsunami is a

series of waves and that the first wave may not be the

most dangerous. The danger from a tsunami can last for

several hours after the arrival of the first wave.

A tsunami surge may be small at one point of the shore and large at another point a short distance

away. Do not assume that because there is minimal sign of a tsunami in one place it will be

like that everywhere else.Tsunamis can travel up rivers and streams that lead to the ocean. Stay away from rivers and streams that lead to the

ocean.

It's always a good idea to keep a store of emergency

supplies that include sufficient medications, water, and other

essentials sufficient for at least 72 hours.

THAT’S THE SCIENCE OF TSUNAMI

TEST YOUR KNOWLEDGE!

GET ¼ SHEET OF PAPER.WRITE YOUR NAME, YR. & SEC. AND DATE TODAY

INSTRUCTION. Supply the needed word/s on the blank to complete the paragraph.

(1)________ are found on land as well as at the bottom of the sea. When an underwater fault suddenly moves, a (2)_________ may be formed. It may occurs after an (3)________. In order for it to be formed the fault movement must be (4)_________, that will disturb the water above. The waves that it generate is so powerful because it involves the whole depth of the (5) ___________.

LET’S CHECK

INSTRUCTION. Supply the needed word/s on the blank to complete the paragraph.

(1)Faults are found on land as well as at the bottom of the sea. When an underwater fault suddenly moves, a (2)tsunami may be formed. It may occurs after an (3) earthquake. In order for it to be formed the fault movement must be (4) vertical, that will disturb the water above. The waves that it generate is so powerful because it involves the whole depth of the (5) ocean/sea.

TASK!

Read pg. 135-136 on your module and answer the following? (Write your answer in a ½ sheet of paper)1. What is the discovery of the scientist by

studying earthquake waves?2. What is an S-wave?3. What is a P-wave?