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10/12/18 Homework Code of Conduct discuss homework but write your - PDF document

Oct 19, 2023 •208 likes •320 views

10/12/18 Homework Code of Conduct discuss homework but write your own HW! discuss homework but do not share workload, i.e. all have to work on ALL problems dont copy and paste material from the web/too much text copied from class

  1. 10/12/18 Homework Code of Conduct • discuss homework but write your own HW! • discuss homework but do not share workload, i.e. all have to work on ALL problems • don’t copy and paste material from the web/too much text copied from class website reduces points! • do not copy homeworks from fellow students! • copied HWs receive 0 credit; repeat offenders will be reported to UCSD SIO15-18: Lecture 7 Earthquake Seismology watch Homework 2 video! “adjusted” Lecture 5 SIO15-18: Lecture 7 Earthquake Seismology 1

  2. 10/12/18 source: wikipedia; SD-UT SIO15-18: Lecture 7 Earthquake Seismology source: wikipedia; SD-UT SIO15-18: Lecture 7 Earthquake Seismology 2

  3. 10/12/18 also made landfall in FL SIO15-18: Lecture 7 Earthquake Seismology source: wikipedia; NOAA POPQUIZ #2 YOUR FULL NAME AND STUDENT ID# no credit if one is missing Compared to long faults, large earthquakes are • less likely • more likely • equally likely on shorter faults? Code of Conduct: you may ask your neighbor you may consult your notes, book, online you may NOT write and/or submit your friend’s popquiz SIO15-18: Lecture 7 Earthquake Seismology 3

  4. 10/12/18 POPQUIZ #3 YOUR NAME AND STUDENT ID# Which of the 3 types of earthquakes USUALLY does not trigger a tsunami? Code of Conduct: you may ask your neighbor you may consult your notes, book, online you may NOT write and/or submit your friend’s popquiz SIO15-18: Lecture 7 Earthquake Seismology P and S Waves are body waves Image: S. Marshak “Earth, Portrait of a Planet” SIO15-18: Lecture 7 Earthquake Seismology 4

  5. 10/12/18 R 1. P first, typically smallest signal 2. S, typically larger (felt by humans) 3. Love 4. Rayleigh, longest/largest wavetrain, most damaging short video 7 on : p wave used in early warning systems seismic waves warning time: up to 1 minute how to locate an earthquake SIO15-18: Lecture 7 Earthquake Seismology R short video 7 on : seismic waves how to locate an earthquake SIO15-18: Lecture 7 Earthquake Seismology 5

  6. 10/12/18 SIO15-18: Lecture 7 Earthquake Seismology from Lecture 2 relaxed relaxed cause force <-> stress loaded loaded response deformation <-> strain Fg = k x x Epot = 1/2 k x x 2 strain is a result of stress Loading a Spring Loading an EQ Fault SIO15-18: Lecture 7 Earthquake Seismology 6

  7. 10/12/18 Fig. 5.18 there is already a fault why don’t blocks move all the time? Friction Stress no EQ Stress Friction EQ! asperities: protrusions that increase friction along a fault EQ: when stresses high enough to overcome friction fault breccia/fault gouge: broken-off, ground up asperities SIO15-18: Lecture 7 Earthquake Seismology fault locked very little creep fault locked very little creep 1. stress builds up; asperities; no motion 2. stress overcomes friction -> EQ + aftershocks 3. slip along fault; stress drop Fig. 5.19 • start from 1) SIO15-18: Lecture 7 Earthquake Seismology 7

  8. 10/12/18 • some history of local seismicity in Seattle/Tacoma area • no recorded history of megathrust EQ • 1700 orphan tsunami in Japan has no corresponding local EQ -> M W =9.0 in Cascadia • recurrence time ~ 300 years • complex aseismic slip and episodic tremors (GPS and seismometers) Fig. 5.21 SIO15-18: Lecture 7 Earthquake Seismology Fig. 5.15 � EQs not regular � recurrence time has a certain probability < 100% source: Abbott “Natural Disasters” SIO15-18: Lecture 7 Earthquake Seismology 8

  9. 10/12/18 Fig. 5.16 � recurrence time varies along same fault source: Abbott “Natural Disasters” Probability of EQ before 2032 • 30% chance for a mag 7 quake before 2032, for most places along SAF prognosis for before 2004 • 90% chance for a mag 6 at Parkfield seismic gap/recurrence SIO15-18: Lecture 7 Earthquake Seismology Fig. 5.17 use seismic gap method � EQ recurrence time � Parkfield EQs remarkably regular in > 100 years � next predicted: 1993 28 September 2004, 10:15 PSDT * #7 late or #8 early??? SIO15-18: Lecture 7 Earthquake Seismology 9

  10. 10/12/18 Fig. 5.17 - Mw= 6.5 December 22, 2003 San Simeon EQ increased stress at Parkfield - made #8 more likely??? - but why did #7 not happen? - EQs can trigger/influence other EQs on nearby faults (1992 Landers/Big Bear) - very large EQs may trigger volcanism far away (Rayleigh waves!) (2002 Denali EQ/Yellowstone; 2004 Sumatra/Alaska volcanoes) SIO15-18: Lecture 7 Earthquake Seismology Fig. 6.43 InSAR: Interferometric Synthetic Aperture Radar • overlay satellite altimetry map before and after EQ • interferogram -> fringes show amount of slip along fault Sep 17, 1999 Izmit, Turkey Earthquake SIO15-18: Lecture 7 Earthquake Seismology Image: NASA/JPL; wikipedia 10

  11. 10/12/18 • example: southern SAF • last major EQ: 250 years ago, while north and middle SAF ruptured 1906 and 1857 • typical co-seismic slip for big EQs: 7-10m relaxed loaded • use stack of INSAR images to get strain rate • extrapolate to 250yrs SIO15-18: Lecture 7 Earthquake Seismology Fig. 6.44 site amplification takes into account local geology probability of strong shaking takes into account local geology, tectonics, seismicity Fig. 6.45 SIO15-18: Lecture 7 Earthquake Seismology 11

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