The first place to get data about any earthquake is the USGS, of course. Their Earthquakes in the Last Seven Days page is a regular visit for me. By going to the World map and clicking on the region of interest, you can then click on the earthquake you are interested in.

Here's the summary page for this devastating quake.

The maps page has lots of good information, including the Historical Seismicity Map:

Also, there is a Scientific and Technical page that contains all sorts of data that helps geologists figure out how the fault moved. Most interesting of all that info is the Finite Fault Model, which shows how the fault moved, or as we say, "slipped".

Here's what the fault movement looked like:

"Figure 1. Cross-section of slip distribution. The strike of fault plane is indicated by the black arrow and the hypocenter location is denoted by the red star, the slip amplitude are shown in color and motion direction of the hanging wall relative to the footwall is indicated by white arrows. Contours show the rupture initiation time in seconds."

What does all this mean? The figure is a view of the ruptured fault plane. Idealized fault plane, really, since these things tend to have a slightly curving shape or other non-planer geometries. "Strike" refers to the bearing of the plane as a compass direction. In this case the fault runs in a direction of 262 degrees, or 8 degrees south of west. Therefore, we are looking at this section from the north. The "dip" is the distance up or down the fault plane. Since this fault has a dip angle of 70 degrees, (measured down from horizontal) we are looking at an inclined fault as well. This also means we are on the "hanging wall" of the fault. The black arrows show how the north side of the fault (hanging wall) moved relative to the south side (footwall). The greatest rupture took place near the hypocenter, with movements of more than 400 cm, or about 14 feet (red shading) Near the surface, the displacement was around 8 feet (green shading), and was mostly a sideways motion, what we call "strikeslip". In this case, since the north side slid west relative to the south side, this would be a "left-lateral motion". However, the west end of the rupture had more of an up-down motion, called "dip-slip". Since the Hanging wall is moving up relative to the footwall, this is a reverse sense of motion. If there is going to be surface evidence of this event, it will most likely to be seen in the area almost 18 clicks west and south of the epicenter. Most aftershocks are expected to take place in the area just outside of the edges of the rupture.

The rupture began at the hypocenter, and moved outward, covering 18 km in about 15 seconds.

Another view of this can be seen in this image, which puts the fault plane in it proper orientation on a map. Note that the figure we've been looking at is upside down in this presentation, and narrower, because we are now looking down at the inclined fault from above, not from the north side.

I think that's pretty cool, but not enough resolution to see what really happened. So I took the USGS image and put it into Google Earth and get this:

(picture no. 191 from the old board's gallery, not restored)

It's not perfect, but it gives us an idea of how the fault moved and where. Just remember that the part of the figure that is to the south is at or near the surface. The areas of the figure that are further north are deeper, the deepest part being 22 km below the surface. You can also see that most of the aftershocks are taking place to the west, suggesting that the rupture was propogating in that direction.

(As a geologist I am interested in the mechanics of what happened. As a human I am horrified by the cost to human lives. Even as I examine the data, those lives are ever in my thoughts.)