Geomorphic, stratigraphic, paleomagnetic, and pedologic data reveal that: (a) the principal phase of the Basin and Range disturbance, sensu strictu, terminated within a latest Miocene to early Pliocene interval (~6 to 3 m.y.B.P) in two basins near Tucson; and (b) general tectonic quiescence has continued in these basins to the present. Approximately correlative relationships in adjacent basins suggest a similarly timed waning of large-scale Basin-Range tectonism throughout most of southeastern Arizona.
The moment magnitude (Mw) 7.9 Fort Tejon earthquake of 1857, with a ~350-kilometer-long surface rupture, was the most recent major earthquake along the south-central San Andreas Fault, California. Based on previous measurements of its surface slip distribution, rupture along the ~60-kilometer-long Carrizo segment was thought to control the recurrence of 1857-like earthquakes.
Increasingly, fault slip rates are being used to constrain earthquake recurrence relationships for site-specific probabilistic seismic hazard (ground motion) assessments. This paper shows the sensitivity of seismic hazard assessments to variations in recurrence models and parameters that incorporate fault slip rates.
After more than a century of research, geologists and other scientists have increased their understanding of the tectonic processes at work in the Wasatch Front and are now beginning to answer the questions about the seismicity and tectonics of the Wasatch Front that Gilbert and others first posed Scientists, engineers, architects, urban planners, and emergency managers are not waiting for a major earthquake disaster to learn that measures must be implemented to mitigate an earthquake's effects.
A paleoseismic study conducted along the Cholame segment of the San Andreas fault provides evidence for three earthquakes and the amount of lateral offset for the most recent event (1857 Fort Tejon earthquake).
The contemporary seismicity of the Colorado Plateau based on seismic monitoring in the past 30 yr can be characterized as being of small to moderate magnitude, and contrary to earlier views, of a low to moderate rate of occurrence with earthquakes widely distributed.