Earthquakes - SECONDARY EARTHQUAKE HAZARDS Flashcards
primary hazard associated with earthquakes
failure of structures
secondary earthquake hazards
liquefaction
ground displacement
ground fissures
earthquake-induced mass wasting
fires
tsunamis
what sediment is prone to liquefaction
sand
what is liquefaction
compacted sand-rich sediments behave like a fluid due to lateral/shear motion
what causes liquefaction
lateral motion increasing the water pressure within pore spaces, preventing vibrating grains from making contact with each other
rocks on either side of a fault move away from each other horizontally or vertically
ground displacement
are large open cracks that typically develop near the surface
ground fissures
ground fissures are developed near the surface where there is little resistance to ______ and _____
rolling and stretching motion
t or f: open fissures affect less number of structures than faults
F (affect more because they occur over a much broader area)
t or f: earthquake trigger mass wasting
t
gas lines are broken and ignited by broken electrical wires in damaged buildings
fire
a series of ocean wave that is formed when energy is suddenly released and transferred into the ocean
tsunami
tsunamis are triggered usually by _____ faulting
thrust
italian seismologist who created an intensity scale
Giuseppe Mercalli, 1902
quantifies earthquakes through first-hand human observations of the damage sustained by buildings
intensity scale
rankings on intensity scale are _____ and ____ such that similar rankings are grouped together
plotted on a map ; contoured
what is PEIS
PHIVOLCS Earthquake Intensity Scale
PEIS was developed as a response to what particular event?
1990 Luzon Earthquake (Mag 7.8)
PEIS replaced what intensity scale on what year?
Rossi-Forel intensity scale on 1996
one of the first seismic scales used to reflect earthquake intensities and was used for about two decades until the introduction of Mercalli scale
Rossi-Forel intensity scale
who developed Rossi-Forel intensity scale?
Michele Stefano de Rossi and Francois Alphonse Forel in the late 19th century
PEIS ranges from
I to X
PEIS
scarcely perceptible
slightly felt
weak
moderately strong
strong
very strong
destructive
very destructive
devastating
completely devastating
quantify the amount of ground shaking and energy released of earthquakes
Magnitude Scales
Richter Magnitude Scale was named after
Charles F. Richter
Richter magnitude scale rates earthquakes based on _______
the size of their seismic waves
what measures the size of seismic waves
seismograph
the size of seismic waves is governed by its:
amplitude (wave height) and distance
scientists discovered that Richter magnitude scale isn’t always consistent with one another, particularly for ______
large-magnitude earthquakes
t or f: moment magnitude scale is based on the similar types of seismogram measurements as Richter’s
T
why is moment magnitude more accurate than richter’s?
because it covers a wide range of geological conditions and magnitude
the total amount of energy released of earthquake based on moment magnitude scale is determined by:
the surface area of the ruptured fault and the vertical/horizontal displacement
a magnitude 7 earthquake is how many times stronger than magnitude 4 in terms of ground shaking
1000x
a magnitude 7 earthquake is how many times stronger than magnitude 4 in terms of energy released
27,000x
san francisco earthquake
1906, Mag 7.8
loma prieta earthquake
October 17, 1989 (Mag 6.9)
indonesian earthquake
December 24, 2004 (Mag 9.1)
classification of earthquakes based on magnitude
great 8 or more
major 7-7.9
strong 6-6.9
moderate 5-5.9
light 4-4.9
minor 2-3.9
micro 1.0-1.9
Abra earthquake
July 27, 2022 (Mag 7.0)
in terms of frequency _____ to _____ types of earthquake magnitude often occur
micro to minor
Moro Gulf Earthquake
August 17, 1976
Mag 8.1
depth: 59km
along cotabato, near sulu trench
12:11 AM
generated a 4.5 km tsunami
Japan earthquake that caused liquefaction
Niigata, Japan (1964)
magnitude 7.5
Taiwan earthquake
1999 , Mag 7.6
