GLG 598: Computers in Geology GIS Assignment 11
Query and processing of vector data with application to Arizona seismic
hazard
Danny Foley
Part 1: Seismic hazard analysis for Flagstaff or Tucson area active faults
An analysis of the active faults within in the area of Flagstaff Arizona was performed
utilizing Arc GIS. The active faults within a 50 km buffer of Flagstaff are represented
below with a detailed geographic map and table of
faults.
Part 2: Active faults and Volcanoes for Arizona
A map of all of the active faults overlain on all Quaternary, Quaternary volcanic, and
Tertiary volcanic rock units in Arizona was produced as represented below.
The active faults are in Mars red, then the Quaternary Volcanic units all in rose red, the
Tertiary volcanic rocks in orange, and then all other Quaternary units in yellow, all over
the shaded relief.
Questions:
Where are the faults that cut Quaternary?
The majority of the faults that cut the Quaternary are associated with Quaternary
volcanism as they are found to be cutting or adjacent to Quaternary volcanics. With few
exceptions such as a few faults around Tucson, ~ > 90 % of the faults are found where
Quaternary volcanics are found. Refer to the next question for where exactly they occur.
Where are the places with the Quaternary volcanism?
Quaternary volcanics are found in four large main outcrops with other minor
smaller outcrops within the area of the SE corner, the Central E, the Central North, and
NW corner. They span from the SE corner of the state through the center up to the NW
corner. If a convex arc line were drawn from the SE corner to NW it would intersect all
Quaternary volcanics. Furthermore, all Qv units appear to be in the copper rich areas of
the state, possibly suggesting the Quaternary volcanism was associated with copper
mineralization.
Where are the places that have Tertiary volcanism?
Tertiary volcanism is just south of all the Quaternary volcanism with the
exception of the SE corner Chirichaua Quaternary volcanism and one isolated Tv outcrop
in the NE. However it is still within a generally trending SE – NW arc, however a much
wider span with more units.
What was the change in local of volcanism from the Tertiary to the Quaternary?
It appears that the Arizona volcanism shifted from south to north going from
Tertiary to Quaternary. Also it appears that the amount of volcanism decreased from the
Tertiary to Quaternary with far less and more isolated Quaternary volcanic deposits
compared to Tertiary volcanics.