Comparison of the Northridge LA (1994) and Sichuan,China (2008) Earthquakes

The Nature of the Hazard.

Northridge, LA (1994) 

Measured 6.7 on the Richter Scale 

Due to a blind thrust fault, this is when the fracture of the fault doesnt reach the earths surface. 

The focus of the fault was approx 17km deep 

Faulting in this area is due to the San Andreas Fault, a conservative plate boundary where the pacific plate is moving northwards parallel next to the North American plate.

Although they are moving in the same direction they are moving at different speeds, the pacific plate is moving at 12cm/yr whereas the North American is moving at 6cm/yr, half the speed. This creates a build up of pressure and friction on the boundary. 

600 aftershockes where recorded, the strongest measuring 5.6Mw

Sichuan,China (2008)

This earthquake reached 7.9Mw when it hit China at 2.30pm on 12 May 2008

Due to the collision of the Indo-Australian plate colliding with the Eurasain plate at a destructive plate boundary. 

The resulting fold mountains are heavily faulted and folded, 

It is a result of a fault line which follows the mountain front seperating the Tibetan Plateu from the flat Sichuan Basin.

It was a reverse thrust fault with a displacement of 5/10 metres. 

The focus was 19km below the surface of the epicentre. The epicentre itself was 80km NW of the province capital. 

Aftershocks continued for up to 6 months after the intial quake, these reached up tho a magnitude of 6. 

Over 42,000 have been recorded. 

The effects 

Northridge, LA (1994) 

(Environmental)

The ground had an uplift of 15cm at its maximum, because of this many rockslides occured, some of these actually blocked mountain roads. 

Minor Liquefaction happened in the LA basin, this lead to an increase in building damage.

Ground cracks where later discovered near the epicentre. 

(Social) 

57 people where killed and 1500 where seriously injured. 

Buliding damage was wide spread with 12500 suffering moderate to serious damage. 

Resulting 20,000 homeless people. 

Gas,electricity and water supplies where damaged. Even…