COMMENT OF THE DAY: A NARROW, GENTLE EARTHQUAKE ZONE ON HOUSTON’S WEST SIDE “. . . The Long Point fault cuts straight through the area, hitting brittmore just south of I-10, crossing saint mary’s just to the west, then going through wycliffe and Wilchester, crossing Kirkwood just south of Memorial. It goes all the way down to around Whittington just west of Dairy Ashford. But if you don’t buy a house directly on the fault, you’ll be fine. Judging from the location of this house and where the Long Point fault map shows the fault, this house should be fine. Its neighbor to the west, maybe not.” [Lost_In_Translation, commenting on Yards of Yard in Britmore Oaks]
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Your headline is correct in its “narrow” and “gentle” adjectives, but less than accurate in the use of “earthquake”. There are geologic faults in “earthquake zones”, but they create havoc because they move abruptly and somewhat randomly. BOOM – 30, or 300, or 30,000 years of stored up motion occurs in the blink of an eye.
The Long Point fault (as well as a bunch of others in the Houston area – don’t think that this area is unique) thanks to the soil and subsurface conditions that prevail on the Gulf Coast moves quietly and pretty much constantly – maybe a total of 1/2 inch or so a year? (A real geologist could probably tell you precisely.) Nothing that will shake your house down, but given enough time, a process that will break up a foundation as surely as one of those big metal wrecking balls.
I would love to see a map of the Longpoint fault (seeing as I own a home in the neighborhood). I suspect it runs pretty close to me, I’ve heard the older neighbors mention it and there are two place on my street were it drops a foot or two. They’re only a couple of yards apart, driving over them feels like going over another speed bump.
[PDF]
Mapping Active Faults in the Houston Area Using LIDAR
http://www.searchanddiscovery.com/…/pdf/…/abstract.engelkemeir.et.al.pd...
I know there is a better map I used to use, but it’s based on the data in the link below.
http://pubs.usgs.gov/mf-maps/mf1136/mf1136/
Fault in Houston are serious enough you don’t want to build on them. The Beltway has an interchange where a support beam had to be extended to avoid a fault.
The new High School in Humble had to adjust it’s location on the lot chosen because a fault.
Exxon (Friendswood Development) who developed several of Houston’s master planned communities (Kingwood, Clear Lake City, etc.) would not build near the fault lines, today the areas are greenbelts and neighborhood pocket parks.
movocelot’s link got cut off…takes me to the main page, not the one about Houston’s fault.
kjb434’s link is way cool…
Here’s a map from the USGS of the southern portion of the Long Point Fault, from just north of I-10 through Memorial and Briar Forest areas:
http://learning.hccs.edu/faculty/dwight.kranz/geol1403/semester-project/regional-map-of-long-point-fault/image_view_fullscreen
I’m a geologist and a homeowner in west Houston and one can clearly see the bending of roads and homes near the fault trace at a number of major crossings: Memorial near West Forest, again on Memorial near Kirkwood, Ashford Parkway near Dairy Ashford and Briar Forest/Dairy Ashford intersection. Houses in neighborhoods such as Nottingham Forest, Wilchester, and Yorkshire near the fault zone often have a foot or more relief on their foundations. Driveways, neighborhood walls, and streets buckle and bend. Compile this with the fact that the growth faults in Houston have multiple splays that are less obvious at the surface and Houston’s clayer soils that expand and contract with moisture, and it’s no surprise that the foundation repair business is booming!