Read the following exert from a USGS report concerning a recent earthquake and answer this question.Special Report: The Hector Mine Earthquake, 10/16/1999A M7.1 earthquake occurred at 2:46 a.m. local time on 10/16/1999.The event was located in a remote, sparsely-populated part of the Mojave Desert of California, approximately 47 miles east-southeast of Barstow and 32 miles north of Joshua Tree (see map next page). The initial magnitude estimate of 7.0 was upgraded to 7.1 on October 18, 1999, based on in-depth analysis of "teleseismic" data recorded worldwide.The earthquake occurred on the Lavic Lake fault, one of a series of north-northwest trending faults through the eastern Mojave shear zone. Geologists from the U.S. Geological Survey and Southern California Earthquake Center were able
to fly over the rupture (which is within the Twenty Nine Palms Marine Base) on the afternoon of October 16 and documented a 40-km long surface rupture. The aerial photos show an apparent maximum offset of 3.8-4.7 meters. These preliminary estimates for both fault length and slip are consistent with expectations for a magnitude 7.0 earthquake, although the slip is perhaps somewhat larger than average. The fault is one of a series of closely spaced, northwest-trending, right-lateral strike slip faults that traverse this portion of the Mojave Desert. Together, these faults within what is termed the Mojave Shear Zone serve to relieve a small portion of the stresses that build up along the boundary between the Pacific and North American tectonic plates.An interesting aspect of the Hector Mine earthquake is that it occurred only 7 years after the 1992 Landers and Joshua Tree earthquakes, which occurred on similar faults within the Mojave Shear Zone. This apparent clustering of earthquakes may be purely coincidental, but scientists are conducting research to see if this kind of earthquake behavior is typical of this region. That is, perhaps many of the Mojave Shear Zone faults produce earthquakes within a short time interval (perhaps spanning several hundred or more years), followed by several thousands of years of quiescence. There was considerable offset caused by this earthquake but little damage caused by this earthquake. Why?
A. The earthquake occurred early in the morning.
B. Stress was relieved along the Mojave Shear Zone.
C. The earthquake epicenter was in a remote location.
D. The earthquake had a shallow focus.
Answer: C
You might also like to view...
In the northern hemisphere, suppose you observe the upper-level winds blowing from the south. In which direction from you is the trough of low pressure?
A. west B. east C. north D. south
Where are continental volcanic arcs found?
a) on the overriding plate near a subduction zone b) on the overriding plate near a mid-ocean ridge c) on the downgoing plate near a subduction zone d) on the downgoing plate near a mid-ocean ridge
What is not true of the backshore?
a. It is a relatively inactive zone. b. It extends to the farthest point that sediment reaches. c. It extends slightly seaward of the berm crest. d. It can include dunes and grasses.
What is the difference between "frozen dew" and "frost"?