Earthquakes III: Earthquake Characteristics, Distribution, and Seismology Cont.
Earthquakes at Transform Boundaries
force: shear
fault: strike-slip
depth range: shallow (most are < 30 miles)
width of zone: often narrow
maximum magnitude: big, but not as large as convergent boundaries
potential for M7
frequency: can be infrequent (long return periods)
risk: depends on location
Transform Boundary: 1999 Izmit Earthquake
turkey
august 17, 1999
m 7.4 and m 7.1 within two weeks
19,000 dead
$20 billion in damages
Earthquakes at Divergent Plate Boundaries
force: tensional
fault: normal
depth range: very shallow
it’s hot (thin lithosphere)
<20 miles (and most in upper three miles)
maximum magnitude: not very big
lithosphere is hot and weak
maximum m6-m7 (rare)
frequency of larger earthquakes: frequent (weak rocks, lots of little earthquakes)
risk: very low for a mid-ocean, undersea ridge
moderate for continental divergent boundaries
Earthquakes III: Earthquake Characteristics, Distribution, and Seismology Cont.
Earthquakes at Transform Boundaries
force: shear
fault: strike-slip
depth range: shallow (most are < 30 miles)
width of zone: often narrow
maximum magnitude: big, but not as large as convergent boundaries
potential for M7
frequency: can be infrequent (long return periods)
risk: depends on location
Transform Boundary: 1999 Izmit Earthquake
turkey
august 17, 1999
m 7.4 and m 7.1 within two weeks
19,000 dead
$20 billion in damages
Earthquakes at Divergent Plate Boundaries
force: tensional
fault: normal
depth range: very shallow
it’s hot (thin lithosphere)
<20 miles (and most in upper three miles)
maximum magnitude: not very big
lithosphere is hot and weak
maximum m6-m7 (rare)
frequency of larger earthquakes: frequent (weak rocks, lots of little earthquakes)
risk: very low for a mid-ocean, undersea ridge
moderate for continental divergent boundaries