Understanding regional tectonics using beach balls Part I: Remember beach balls and fault types Figure 1 shows that we can distinguish the different types of faults (normal, reverse and strike- slip) using beach balls. Beach balls describe the focal mechanism occurring at a given fault. Figure 1: Different types of faults and associated focal mechanisms. The black parts are under compression and the white parts under tension. For the strike-slip faults, the circle with the cross means that the block is sliding further from you, while the dot inside the circle means that the block is sliding towards you. For all three cases, the direction of the fault is through the page. Part II: Using beach balls to understand the regional tectonics around Turkey Figure 2 shows the focal mechanisms for the eastern Mediterranean region. 1) Draw arrows showing the relative motion across some of the main fault zones (shown with eleven pairs of dots), using the beach balls on Figure 2 and help from Figure 1 . Note that for strike-slip faults, there are usually two possibilities (eg., left-lateral strike slip fault oriented N-S or right-lateral strike-slip fault oriented W-E). However, here, you already have the direction of the fault, so there is only one possibility. 2) Draw arrows showing the motion of the three southern plates relative to Eurasia. That means that Eurasia, in this exercise, is not moving Motion of the three southern plates are shown with four boxes. A good way to work this problem is to imagine cutting the map on the next page map into pieces along the plate-bounding faults, tape Eurasian to a table, and try sliding the blocks to see if you can find a way to move them that is consistent with the focal mechanisms. Figure 2, next page: (top). Focal mechanisms for the eastern Mediterranean region. (bottom) Topographic and bathymetric maps to be completed with relative motions of the plates. There are volcanoes on near the west-most box. Why is this? 4) Compare the African and Arabian arrows (i.e, velocity vectors). Which is larger? 5) There are large mountains in Iran and the Caucuses (in the NE portion of the map, see also name of countries on Figure 4). Why is this? 6) There are elongated islands, peninsulas and inlets in Greece that trend SE-NW to E-W. Why is this? Figure 3: Major faults in the Mediterranean region..

1. Understanding regional tectonics using beach balls Part I: Remember beach balls and fault types
Figure 1 shows that we can distinguish the different types of faults (normal, reverse and strike-
slip) using beach balls. Beach balls describe the focal mechanism occurring at a given fault.
Figure 1: Different types of faults and associated focal mechanisms. The black parts are under
compression and the white parts under tension. For the strike-slip faults, the circle with the cross
means that the block is sliding further from you, while the dot inside the circle means that the
block is sliding towards you. For all three cases, the direction of the fault is through the page.
Part II: Using beach balls to understand the regional tectonics around Turkey Figure 2 shows the
focal mechanisms for the eastern Mediterranean region. 1) Draw arrows showing the relative
motion across some of the main fault zones (shown with eleven pairs of dots), using the beach
balls on Figure 2 and help from Figure 1 . Note that for strike-slip faults, there are usually two
possibilities (eg., left-lateral strike slip fault oriented N-S or right-lateral strike-slip fault oriented
W-E). However, here, you already have the direction of the fault, so there is only one possibility.
2) Draw arrows showing the motion of the three southern plates relative to Eurasia. That means
that Eurasia, in this exercise, is not moving Motion of the three southern plates are shown with
four boxes. A good way to work this problem is to imagine cutting the map on the next page map
into pieces along the plate-bounding faults, tape Eurasian to a table, and try sliding the blocks to
see if you can find a way to move them that is consistent with the focal mechanisms. Figure 2,
next page: (top). Focal mechanisms for the eastern Mediterranean region. (bottom) Topographic
and bathymetric maps to be completed with relative motions of the plates.
There are volcanoes on near the west-most box. Why is this? 4) Compare the African and
Arabian arrows (i.e, velocity vectors). Which is larger? 5) There are large mountains in Iran and
the Caucuses (in the NE portion of the map, see also name of countries on Figure 4). Why is
this? 6) There are elongated islands, peninsulas and inlets in Greece that trend SE-NW to E-W.
Why is this?
Figure 3: Major faults in the Mediterranean region.