markhaldane

For those interested, a summary of the Haiti earthquake via USGS: Magnitude 7.0 Depth 13 km Located on the boundary between the Caribbean Plate and North-American Plate (left-lateral strike-slip). This boundary accomodates 20 mm/y movement. Earthquake mechanism was a left-lateral strike-slip fault on the Enriquillo-Plantain Garden fault system (7 mm/y movement). There is a nice poster with some maps here. Off-topic; Is this place likely to get an Earth-Sciences sub-forum anytime soon?

Do you mean fault planes? If so, then yes; faults which are no longer tectonically active are very common. In geology the term "discontinuity" is used to describe the boundaries between layers in the Earth's interior where the velocities of seismic waves change. For example, the boundary between the crust and the mantle is known as the Mohorovičić discontinuity, and is defined by an increase in seismic wave speed (mainly P-waves I think). There is no "tectonic" activity at these boundaries.

I've recently completed a module using Arc GIS as part of a larger "Remote Sensing" overview. Whether I can help or not depends on what you actually need..?

Hi Proteus, I hope this answer is still valid for you. To start, lodestone is actually the name for the naturally magnetised version of the mineral magnetite (Fe3O4) which, to answer the second part of your question, is also probably the most widespread (or at least most commonly found at the surface; I don't know crustal abundances of these minerals) magnetic mineral. Another common magnetic mineral is pyrrhotite (Fe1-xS, where x = 0 through to 0.2). The magnetism of pyrrhotite increases with decreasing iron content. The FeS end-member is called troilite and is non-magnetic (troilite is not a commonly occuring mineral). Other weakly magnetic minerals that I can think of at the moment include; Chromite ((Fe, Mg)Cr2O4) and Ilmenite (FeTiO3)