Indian Ocean Earthquake

Dec. 26, 2004

Earthquake• As many of us were sitting down to

Christmas dinner (4:58 p.m. Dec. 25th Victoria time) the largest earthquake in 40 years the hit the Indian Ocean

• At 7:58 a.m. local time on Dec. 26, 2004 a magnitude 9.3 earthquake occurred off the coast of Indonesia (initially measured as 9.0)

• The focus was 30 km below the ocean floor

Although the earthquake’s epicentre was in the Indian Ocean, the region is in the edge of the “Ring of Fire”

Location of Epicentre in Indian Ocean

• The earthquake set off a series of aftershocks as the plate boundary continued to shift.

• At least 15 aftershocks between magnitudes 5.8 and 7.3 happened in the next 12 hours

• Aftershocks continued for months as the plates settled into their new positions

• From this info, scientists have estimated that the rupture zone was over 1200 km long and up to 100 km wide, with most of the movement in the southernmost 400 km of that zone

• At the focus, it is estimated that the plates moved about 20 m

• The ocean floor moved about 10 m WSW and was uplifted several metres

Tectonic Plates and

Aftershocks

1 Month of Aftershocks

Epicentre

Epicentre

Previous Earthquakes

Earthquakes in area since 1900

Previous Tsunamis

Previous Tsunamis in Area

• Within hours tsunamis had hit coastal areas around the Indian Ocean as far away as 4500 km from the epicentre

• Within the next few days, the enormity of the disaster grew as more information came in from areas hit

Countries Affected

Hours after Earthquake

Time for Tsunami Indian Ocean

Animation (5 hours)

Local Animation

Full Indian Ocean

Animation

• This horror is ongoing for those in the path of the devastation as over 1 million people are left homeless, surrounded by death and destructions without safe drinking water, food or sanitation

• The death toll has surpassed 200,000 people and could reach 300,000 as more bodies are found.

• Humanitarian aid poured into the area to help rebuild and stop the spread of disease which could sweep these areas

Before & after of a village in

Aceh, Sumatra

Indonesia

Before & After Images from Indonesia

• View Images

March 28, 2005

• Another large earthquake (magnitude 8.7) hit off the coast of Sumatra (approx 300 km south east of the December quake)

March 28, 2005

How far inland could a tsunami travel?

Not only is the wave large, but the land itself can drop as a result of the earthquake

This is called subsidence

It Could Happen Here

• The boundary of the Juan de Fuca and Pacific Plate (called the Cascadia Subduction Zone) is a similar type of boundary

• Historical records indicate that a similar “megathrust”earthquake of magnitude 9 happened here in the year 1700