The Great Hanshin Earthquake: Kobe, Japan

1
The Great Hanshin Earthquake Kobe, Japan

• Rajan Katru
• ESS 315 Environmental Geology

2
Tectonic Setting

• Japan is part of a setting where there is an
  intersection of three tectonic plates Pacific,
  Eurasian, and Philippine.
• This Triple Junction is a junction of three
  compressive Subduction Zones. Even though the
  city of Kobe is located away from the
  intersection of these plates, it is in a zone of
  strike slip faults.
• The red hatched areas indicate the part of the
  subduction faults that had been broken in the
  great earthquakes of 1944 and 1946.
• A strike-slip fault is where the fault surface is
  usually near vertical and the footwall moves
  either left or right lateral with very little
  vertical movement.

3
Fault Motion/Characteristics

• This map on the left shows the epicenters of the
  earthquake's aftershocks within the first two
  days afterward.
• The most reliable way to locate the fault that
  broke in any earthquake is to observe where
  aftershocks are concentrated.
• The earthquake fault obliquely cut the north side
  of Awaji Island, and crossed the bay to run along
  the Honshu coast directly below the city of Kobe.

• Magnitude 6.9
• A surface rupture of the fault was observed only
  in a rural area of Awaji Island, with
  displacements of up to 3 meters
• From left to right along the rupture, a landslide
  from the rupture covers a road a fault scarp
  across a rice paddy a right-lateral offset in a
  dirt road and three more pointers to the scarp.

4
Elastic Rebound- The permanent deformation of the
ground due to the fault rupture. This will extend
many kilometers from the fault itself, and is
usually measurable even where the rupture itself
remains buried.

• The map image above of Awaji Island shows eight
  or more colored interference fringe lines
  approaching the fault, at 11 cm of vertical
  displacement per fringe contour, demonstrating
  almost 1 meter of uplift by the earthquake.
• Top right shows two fringes parallel the coast
  through the city of Kobe, Showing about 20 cm of
  displacement across the city from the buried
  fault.

5
Damage

• Over 5,000 killed, and 26,000 injured.
• Economic loss due estimated up to 200 billion US
  dollars.
• Many wooden structures collapsed due to shear and
  the popular use of heavy tile roofs.
• Many lifelines such as roadways, utilities, and
  railways were destroyed. This delayed many rescue
  efforts.
• Low land areas of softer, water saturated soils
  experienced the most destructions. (liquefaction)
• Due to broken gas lines, large sections of the
  city burned, greatly contributed to loss of life.
  

6
Lessons Learned

• The earthquake was a wake-up call to the Japanese
  disaster preventions authorities.
• They re-evaluated their construction techniques
  to prevent collapsing buildings and bridges.
• Infrastructure and Transport began designating
  special disaster prevention routes and
  reinforcing the roads and surrounding buildings
  so as to keep them as intact as possible in the
  event of another earthquake.
• The response to the 2004 Chuetsu earthquake was
  significantly faster and more effective.