geology 15 mid term ii review. focal mechanisms are diagrams made from first motion seismologic...
TRANSCRIPT
Geology 15 Mid Term II Review
Focal mechanisms are diagrams made from first motion seismologic records that show the possible motion on a fault, and the possible sense of motion on that fault. There are two possible fault planes for each focal mechanism.
http://earthquake.usgs.gov/earthquakes/world/10_largest_world.php
M = 7.1
Table 1. Earthquake Chronology Hokey Poky fault, Oregon, USA.
Earthquake Number
Site A Site B Site C Site D
Age (yrs AD) RI
Age (yrs AD) RI
Age (yrs AD) RI
Age (yrs AD) RI
1 1857286
185745
185745
1812108
2 1571187
1812265
1812127
1704145
3 1384107
1547187
1685149
1559122
4 1277199
1360276
153649
1437124
5 1078479
108417
1487127
1313140
6 599
1067111
136096
1173242
7 956
1141264
148931
8 842
781116
100 9
764119
1016166
10 645
850
69 11
781
59 12
722
25 13
697
63 14
634
101 15
533
Average RI 252 135 95 147
this year 2013 2013 2013 2013
next expected EQ 2109 1992 1952 1959time span 1258 1212 1324 881
Is the average Recurrence Interval about the same for each site? NO
What can the Recurrence Interval say about this fault?(1) earthquakes did not rupture through each site for each earthquake for some reason. (2) the time between earthquakes varies so that we can interpret this fault to be uncharacteristic and unpredictable. (3) the RI at site C is much shorter than the RI of A. (4) the RI at sites B and D are intermediate compared to sites A and C.
Which sites (A, B, C, or D) are more “due” for an earthquake?Adding the average RI to the age of the most recent earthquake gives us an estimate for when the next earthquake might occur ("next expected"). The first expected earthquake was at site C, then site D, site B, and lastly site A.
Is the average Recurrence Interval about the same for each site? NO
What can the Recurrence Interval say about this fault?(1) earthquakes did not rupture through each site for each earthquake for some reason. (2) the time between earthquakes varies so that we can interpret this fault to be uncharacteristic and unpredictable. (3) the RI at site C is much shorter than the RI of A. (4) the RI at sites B and D are intermediate compared to sites A and C. (5) the earthquakes that occur at all sites probably represent larger earthquakes. (6) the fault has different places that are more resistant to slipping (more friction) and this may make the fault slip at different rates.Which sites (A, B, C, or D) are more “due” for an earthquake?Adding the average RI to the age of the most recent earthquake gives us an estimate for when the next earthquake might occur ("next expected"). The first expected earthquake was at site C, then site D, site B, and lastly site A.