Week 7: Seismology
Earthquake distribu8ons • Discussion of depth, magnitude, geographical distribu6ons
of one-‐year NEIC earthquake data sets from 2016, 2015, 2014 etc
Focal Mechanisms • Basic “beach ball” paHerns for strike-‐slip, normal, thrust,
oblique earthquakes • Inferring strike, dip of fault plane and the strike of the
horizontal component of a slip vector
Seismicity Distribu6ons -‐ your figures…….
Seismicity Distribu6ons: my figures
c.f. Fig 4.10a, text book
c.f. Fig 4.10a, text book
c.f. Fig 4.10b, text book but we have mix of mag types
Seismicity Distribu6ons: my figures
Earthquake magnitudes -‐ discussion
A. Strike slip B. Normal C. Thrust D. Oblique
Focal Mechanism Solu8ons Aka Beach Balls
“Clicker Ques8ons”
What are the strike and dip of the possible fault planes in i) ii) iv)
Focal Mechanism Solu8ons Aka Beach Balls
• hHps://www.youtube.com/watch?v=MomVOkyDdLo
Focal Mechanism Solu8ons Aka Beach Balls
• Fault plane ambigui6es: different solu6ons for N / T / SS
Loca8on Focal mechanism (i-‐iv) and reason
A
B
C
D
The four focal mechanisms below the map (i-iv) correspond to the earthquakes; each might occur 0, 1, 2, or 3 times. Complete the table.
Focal Mechanism Solu8ons Aka Beach Balls
• More visuals for how the projec6ons from the lower focal hemisphere work