Geohazard

The probability of occurrence in a specific period of time and a given area of potentially damage phenomenon

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Type of  Geohazards

•    Earth movement : fault and earthquake
•    Tsunami : underwater earthquake
•    High wind velocity
•    Floods
•    Landslides
•    Volcanic activities
•    Extreme precipitation

  

Earthquake : fault and tsunami

# Earthquake is sudden shaking of the ground due to sudden movement of the earth crust

# “shaking” due to transmission of energy released in the form of seismic waves

#The more energy released, the stronger the quake

# Its originate from focal point/ hypocenter and transmited waves to the surface of the earth. (epicentre)

# Epicentre is the point on the earth surface directly above the hypocenter and are determine by triangulation of atleast        three different seismic stations.

# Seismic waves

Vibrational waves spread outward initially from the focus of an earthquake, and continue to radiate from elsewhere on the fault as rupture proceeds.

The more energy released, the stronger the quake

 Tsunami : underwater earthquake

 # Tsunami is high waves resulted from underwater earthquake

Extreme precipitation

hujan air batu di Jerantut 2009

Volcanic activities

Recent volcanic activity : Sakurajima volcano (Kyushu),Japan 
[13 June 2013 - 28 Aug 2013]

# the volcano has woken up violently with 3 powerful explosions

# The eruption appears to be one of the largest explosions for a long time, producing an ash plume rising to 16-20,000 ft (5-6 km) altitude. 

# An SO2 plume is also visible on satellite data.

# On average, 4-5 explosions have occurred per day, with at least 5 stronger ones producing ash plumes to 10-12,000 ft (3-3.6 km) altitude.

  # Ash wafted as high as 5 kilometers (3 miles) above the Sakurajima volcano in the southern city of Kagoshima on Sunday afternoon, forming its highest plume since the Japan Meteorological Agency started keeping records in 2006.

# Residents wore masks and raincoats and used umbrellas to shield themselves from the falling ash. Drivers turned on their headlights in the dull evening gloom, and railway service in the city was halted temporarily so ash could be removed from the tracks.

# Japan is on the "Ring of Fire," the seismic faults encircling the Pacific Ocean, and has frequent earthquakes and volcanic activity.

 High wind velocity

Hurricane Sandy
October 22, 2012 – October 31, 2012

# The beaches and dunes on Fire Island were severely eroded during Hurricane Sandy.

# Landward shift of the upper portion of the beach averaged 19.7 meters (m) but varied substantially along the coast.

# Hurricane Sandy profoundly impacted the morphology of Fire Island and resulted in an extremely low elevation, low relief configuration that has left the barrier island vulnerable to future storms.

  Floods
Kajang Hit By [Flash Floods]
 (DEC 02, 2011 & SEPT 5, 2012)

# The increased water volume caused nearby Sungai Langat and Sungai Semenyih to break their banks.

# As water levels in the rivers passed the dangerous mark, hundreds of shops and homes in the area were forced to close and move  their goods and belongings to higher ground.

# Geologist believe the factor causing the floods is because of straighten of the original river

# Straitened rivers increase the risk of flooding downstream. A straight river or stream holds less water per distance unit of valley floor than a natural and curvy river. In a rain event a natural curvy river will hold more water.

# it velocity is slowed by the curves of a natural river

# Furthermore, the loss of flood planes by building levies causes rivers to rise higher during flood events and again delivers more water downstream in a short amount of time. 

 New Straits Times http://www.nst.com.my/top-news/kajang


~PROUD TO BE GEOLOGIST~