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10/11/17

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SIO15-17: Lecture 6 Earthquake Hazards


10/6/17 Lecture 4: Santa Ana Predicted for weekend but no red flag warning

Santa Ana•  high temperatures•  low humidity•  high winds

www.weather.gov

Santa Ana winds arecalled Diablo windsin NorCal

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•  should a Red Flag warning have been issued?•  would it have helped?

www.weather.gov late Monday


www.weather.govlate Sunday

Santa Ana winds are called Diablo winds in NorCal

Homework 1/Earthwatch: Sep heat wave devastated grapevines

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•  > 3.5 Mio per year•  small events often•  large events rare


E.g. 3 Mio EQ/year -> 1 EQ every 10.5s 0.3 EQ/year -> 1 EQ every 3.3 years

Fig. 5.13

Get recurrence time from # of EQ per year

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Northridge, CA 01/17/94; 4:31 PST

Mag. 6.772 fatalities$12.5 billion damage1g ground acceleration

Hawaii 10/15/06; 7:07 HST

Source: wikipedia.org

Mag. 6.70 fatalitieslandslides on Hawaii$200 Mio damage (61 buildings)power outage on Oahu

Fig. 1.2 (study guide) Fig. 6.1b


Bam, Iran 12/26/03; 5:26 local time

Mag. 6.6at least 26,000 fatalitiesdisplaced 90% of residentsdestroyed 70% of modern city

Northridge, CA 01/17/94; 4:31 PST

Source: wikipedia.org

Mag. 6.772 fatalities$12.5 billion damagedamaged major freeway

Fig. 1.x

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Image: S. Marshak “Earth, Portrait of a Planet”

brick

Fig. 6.2b

!  60% of old, poorly-built structures collapsed!  structures built after 1984 survived!  1000 fatalities!  poor soil (old land fill sites or steep slopes)!  lack of urban planning and land studies


Fig. 6.2b

Source: Wikipedia

!  sedimentary basin/ancient lake fill!  90% of destroyed buildings built BEFORE 1985

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Sumatra-Andaman 26 Dec 2004•  Mw=9.1; 10m tsunami •  3rd largest EQ in 100 years•  > 240,000 fatalities•  in ocean, along subduction zone

Tohoku 11 Mar 2011•  Mw=9.0; 40m tsunami •  4th largest EQ in 100 years•  < 20,000 fatalities•  in ocean, along subduction zone

Fig. 6.11 Fig. 6.13

source:Wikipediasource:Wikipedia


SIO Pier Dec 27 and Dec 29 2006

shallow-water waves(D < λ/20)particle motion elliptical

deep-water waves(D > λ/2)waves do not sense bottomparticle motion circular v = λ/T or v=g T/(2π)

Chapter 6 (incomplete)

λ  from cm to n100 m

wave height depends on •  wind speed•  duration of wind•  fetch

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SIO15-17: Lecture 6 Earthquake HazardsImage: S. Marshak “Earth, Portrait of a Planet”

•  720-800 km/h!!!•  not noticeable at sea•  built up coming on shore ( >10m)•  15 min between peak and trough

v=√10ms-2•4000m=200m/s=720km/h

Fig. 6.17

•  caused by submarine EQs with vertical displacement•  extremely long wavelength (200 km)•  shallow-water waves -> speed depends on water depth D


Fig. 6.15

Parking Meters in Hilo, HI

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•  tsunami take about 6.5h from Alaska to HI•  “ 14h from Chile to HI

source: wikipedia/USGS

Fig. 6.23


Fig. 6.23

!  people ignore warning!  people forget what to do

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Source: NOAA

! partial warning system! critical components missing! sporadic tsunami history! poor tsunami education

Fig. 6.20

26 December 2004 Sumatra-Andaman Tsunami


29 September 2009Samoa TsunamiSource: NOAA

!  watch tide calendar! flee when low tide suspicious!  you have at least 15min

!  flee when there was an EQ and you are within 1mi of beach!  you have at least 15min

If you felt an EQ

If EQ was distant

stay away from beach for many hours!!!

Fig. 6.24

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2010 Tsunami Warning and Preparedness Report by NRC (9/27/10 LA Times)“since 2004 NOAA improved ability to detect and forecast tsunami”“many coastal communities in U.S. still face challenges in responding to a tsunamithat arrives less that 1h after triggering event”“tsunami rare enough to give false sense of security”“if source is close to shore [only minutes to tsunami] public needs to recognize natural cues”

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