Baby on the Way!

Yep, we're having a baby in June and couldn't be more excited!

The wise man built his house upon a rock, the foolish man built his house on a fault scarp or near a landslide

 I am working on my Masters in Geology. For part of my thesis project I am producing a geomorphic map of the Nephi segment of the Wasatch fault. The Wasatch fault extends from southern Idaho to central Utah along the Wasatch mountain front. It is broken into segments that are ~25 miles long with the Nephi segment running from Santaquin to Nephi (~40 miles south of Provo). The Wasatch fault is an active normal fault (depicted below).

In the case of the Wasatch fault the foot wall would be the Wasatch Mtns. and the hanging wall would be the valleys to the west of the mountains (Salt Lake, Utah, etc.) When faulting occurs the hanging wall drops down with respect to the foot wall.

I am using a LIDAR data set to produce my geomoprhic map. LIDAR stands for light detection and ranging. If this sounds a lot like RADAR it's because it is. A lidar image is produced by flying an airplane over your study area. The airplane has a laser on board that it sweeps over the land surface as it flies overhead.

The plane's position is continuously tracked by a GPS unit within the plane. Ground control points are also continuously monitored by GPS during data acquisition. The laser is reflected off the ground surface and returns to the airplane. These returns go through some computations using the time it took the laser to hit the ground surface and return, the laser's shot angle, and the plane's position to determine x,y,z coordinates for each return. This yields a grid of points that model the ground surface topography. One of the coolest things about lidar is that one is able to remove laser returns caused by vegetation. This leaves a model of the bare ground surface with vegetation removed. This can be very useful to pick out very subtle geomorphic features. After some fancy processing magic these data points yield an image of the ground surface (shown below is a lidar image of a portion of my study area).

I use this image to map various geomorphic features such as fault scarps (in the above image the fault scarp is the steep shaded slope running along the base of the mountain highlighted by the red arrows), landslides, debris flows, etc. This kind of map can be very useful for city planning and development. Let me illustrate this idea. If you build your house on a fault and an earthquake occurs this is what your house will look like.

Fortunately this hasn't happened here in Utah yet, but it is a very real possibility. If you build your house near a landslide then your backyard may look like this after a particularly wet spring.

This is damage from a landslide up City Creek Canyon near Salt Lake City. Notice the fence in the bottom of the picture. That was running along the back boundary of this house's backyard. It is now 30 ft. lower and significantly farther away from the house. I wonder if he still gets good satellite reception?

It is only a matter of time before the rest of the house joins the satellite dish. This landslide was active and documented long before this house was ever built. The moral of the story is the wise man or woman makes sure they understand the potential geologic hazards before they build or buy a house.