plate motions
TRANSCRIPT
Solid Earth Geophysics
Department of Earth SciencesKFUPM
Today’s class: Plate MotionsReading: Fowler Chapters 2-3
http://neic.usgs.gov/neis/plate_tectonics/plates.html
http://www2.nature.nps.gov/geology/usgsnps/animate/A14.gif
Continental Drift
1) Begins with view of Earth with continents in their present positions, 2) continents move back in time to reunite as Pangaea, 3) Pangaea label appears, 4) Locations of stratigraphic and fossil evidence that Wegener used to argue in favor of continental drift is added.
www.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml
Plates and plate boundaries
passive margin
transform margin
convergent margin
divergent margin
May 12, 2007
Periods of passive: Stress builds up between plates.Periods of active: stress is released, earthquakes
Magnitude 7.9 – USGS Date: May 12, 2008 Hour: 14:28:00 local time Location : 31.021N, 103.367E Focal depth: 10 km Imax=9
May 12, 2008 M7.9
Station: ENH - Enshi, Hubei Province, China
Seismicity Faulting
Many earthquakes in China were caused by the continental collision between India and Tibet
The May 12, 2008 earthquake (hand-drawn black star) occurred along the Long MenShan fault, which was responsible for magnitude ~6 quakes over the past ~400 years.
A more active fault at the north of the May 12 quake in the SongPan area produced stronger quakes including the 7.2 in 1976 and 7.5 in 1933
Courtesy: Zhenming Wang, PhD, PE, Kentucky Geological Survey, 2007
Aftershocks
Over the past 30 hours a total of 46 magnitude >= 3.5 quakes have occurred. Most of the aftershocks are on the NE part of the mainshock.The largest aftershock is an 6.0 occurred 15 minutes after the mainshock
WHAT IS PLATE TECTONICS?
Topography Earthquakes
VolcanoesHeat Flow