Hands-on manipulative Teaching Aid:
Once finished, the global focal mechanism allows a clear visual presentation. Re-orienting the globe shows how traditional "beach ball" pictures of different focal mechanisms (normal, reverse, strike-slip, oblique slip) are actually all the same, but just oriented differently. Spatial relations between nodal planes, P- and T-axes and slip vectors are much easier to demonstrate in three dimensions.
***Build-It-yourself Lab Kit includes:
Matte-finish self adhesive Dry-Erase Map gores to place on
***Octant "Wedges" with equator magnets to build sphere.
***assembly instructions on DVD
***Dry-erase Schmidt Net foam core workboard with plain white
reverse side also Dry-erase
***two exterior auxiliary planes, "Spherical rulers)
***Clear 18" dry erase hemisphere with alignment stickers to
adhere included clear vinyl self adhesive grid pattern
and equator tick marks
Assembled Grid Globe---plot arrival data at globe locations corresponding to latitude and longitude of seismic stations. Closed circles indicate first "upward" motion, open circles indicate first "downward" motion. After plotting arrival data, use the spherical ruler to trace great circles separating regions of open circles from regions of closed circles. Use the protractor to draw a perpendicular to the great circle. To finish delineating open-circle and closed-circle quadrants, use the spherical ruler to draw a great circle through the perpendicular marks. This results in finished Focal Mechanism Solution, showing compressional (shaded, closed circle) quadrants and dilatational quadrants.
Clear Hemisphere & Stereonet workboard---The Schmidt Net is a 2D representation of the lower hemisphere of the globe. The clear hemisphere allows visualization by drawing points and great circles (from above exercise) on it, showing how they project down to the workboard.
see additional lab activities in attached links, courtest Dyanthe Weeraratne, Cal State Northridge: