Test 2 Flashcards
What was the 1 in 1000 year flood event and where did it happen
- South Carolina
- multiple days of torrential rain fall- the long duration of high water put pressure on and weakened the earthen dams
- resulted in 14 dam failures, monitoring $$$
- more than 10 deaths
- AKA Natural Disaster
Historical Precipitation in NC
-Oct. 4=record rainfall was 5.19 inches in one day (2015)
Europe predicted Joaquin would
remain in the ocean (correct)
What physical evidence do we have to prove past tsunamis and the numerical model of a future event (Cascadia)
- Cascadia (subduction zone) (NOAA)
- Last time it occurred was in 1700s with Native Americans
- Deposition of sand attributed to tsunami, followed by tidal muds
- Geological evidence when it happened
P waves are also known as ___ and are _____ waves that travel fastest through ______
- PRIMARY waves
- compressional waves, travel fastest through all physical states of media (liquids, solids, and gases)
P waves metaphor
like a slinky, energy directed towards travel
IIIWWW
——–> (energy)
S wave
- SECONDARY waves
- known as shear waves
- travel slower than P waves
- travel faster than surface waves
S waves can only propagate or travel through
solid materials
R waves are commonly known as
surface waves
Surface waves
- move along the earth’s surface
- travels slowest, but causes the most damage
- much like an ocean wave
- rolling motion
Surface waves cause most damage to
buildings
Frequency is the number of
cycles per second
Frequency is measured in
Hertz (hz) or cycles per second
High frequency causes
low buildings to shake
Low frequency causes
tall buildings to vibrate
Location of earthquake is determined by
-expanding seismic wave front and multiple seismometers
High Frequency
- a lot of cycles in a short amount of time (fast cycling shakes low buildings)
- Does not damage tall buildings
Energy is lost much faster with
high frequency
Low Frequency
-less energy loss, extends further from the point of earthquake
Earth Materials and shaking amplifications
o Hard Igneous (harder) o Sed rock (hard) o Alluvium (weak rock) o Silt, Mud (weakest rock) -surface waves
Amplification goes further through___
-harder rock (igneous, sedimentary)
Amplification goes slower but shakes with
-weaker rock (alluvium, silt)
low amplification in
hard rocks
high amplification in
weak rocks
1985 Mexico City
- Mexico city located on top of lake beds resulted in serious damage
- Most densely populated city in the world
EQ in San Francisco
- Bay bridge and cypress highway
- structural damage indicated they built bridge on soft mud
- Damage occurs in areas on top of soft mud (amplification much stronger)
Earthquake cycle
- Time 1: no strain, no displacement, material being deposited, no serious activity
- Time 2: elastic strain begins (rocks begin to bend)
- Time 3: elastic strain accumulates (rocks bend more)
- Time 4: (displacement/fault) Rupture occurs and rocks rebound, elastic strain is replaced by horizontal displacement known as fault slip
During what stage of the earthquake cycle do rocks separate
-Time 3
Causes of Human Induced EQ
- (much smaller mag)
- loading: building a dam or heavy structures
- waste disposal via wells
- underground explosions (includes nuclear explosions)
Denver, Colorado human induced EQ
- Earthquakes began to increase over time after use of disposal well
- No direct proof
- Correlation: no waste injected=little quake activity, as injections increases quake activity increased
Hydraulic fracturing and EQs
o Controversial
o Waste water injection may cause ground to move
o Links earthquakes to fracking
Effects of EQs
- Ground shaking, tilting, and ground rupture
- Loss of life and collapse of infrastructure
- Fires and liquefaction
- Landslides
- Health issues
Alaskan landslide
-2002, magnitude 7.9
El Salvador EQ
- Jan, 2001
- 500 dead
1995 Japan Earthquake
-Kobe
Long-term EQ prediction
-earthquake hazard risk mapping
Short term EQ prediction
- Frequency and distribution pattern of foreshocks
- Deformation of the ground surface: Tilting, elevation changes
- Emission of radon gas from rocks
- Seismic gap along faults
- Abnormal animal activities
Etho-Geological Forecasting
Unusual Animal Behavior & Earthquake Prediction
Response to EQ hazards
- Site selection for critical facilities
- Structure reinforcement and protection
- Land-use regulation and planning, structures
- Emergency planning and management: Insurance and relief measures
- Warning systems (time, reliability)
- Education (pre-, during & post event)
What does tsunami mean in japanese
large harbor waves
Tsunamis are produced by the
sudden vertical displacement of ocean water
Tsunamis are triggered by
- any rapid uplift or subsidence of the seafloor, such as
- submarine earthquake (most),
- landslide,
- volcanism, collapse
- impact of asteroid or comet (mega-tsunami – low frequency)
Indonesian Tsunami occurred on _____ and within a few hours, close to ________ people were killed
- December 26, 2004
- within a few hours, close to 250,000 people were killed
- No warning system in place (30 mins could have saved thousands of lives)
Indonesian Tsunami facts
- Largest earthquake on Earth in the past 40 yrs
- M 9.1
- A large amount of displacement along the thrust faults in the subduction zone, classified as “megathrust event”
- The total length of the rupture over 1500 km (930 mi)
megathrust event
- a large amount of displacement along the thrust faults in the subduction zone
- ex: Indonesian tsunami
four stage process of the Tsunamigenesis
(starts with vertical displacement)
- EQ rupture in seafloor pushes water upward
- tsunami moves rapidly in deep ocean (over 500 km/hr)
- as tsunami nears land it slows to around 45 km/hr but is squeezed upward generating height
- tsunami heads inland destroying everything in path
In the fourth stage of the tsunamigenesis
the trough of wave may arrive first, exposing the seafloor
Distant tsunami
Travels out across the deep ocean at high speed for thousands of kilometers to strike remote shorelines with very little loss of energy
Local tsunami
Heads in the opposite direction toward the nearby land and arrives quickly following an earthquake
Each (distant and local) tsunami has a wave height
~ ½ of that of the original dome of water
Submarine landslides
can generate very large tsunamis
Lituya Bay, Alaska (1958)
- highest known mega-tsunami
- The landslide set in motion by a M 7.7 earthquake on a nearby fault.
- Caused waters in the bay to surge upward to an elevation of about 524 m (1700’) above the normal water level
Greatest risk of tsunami (location)
- Coasts close to a major subduction zone or directly across the ocean basin from a major subduction zone are at greatest risk
- The greatest tsunami hazard with return periods of several hundred years
High risk tsunami regions
The Cascadia subduction zone, the Chilean trench, the subduction zones off the coast of Japan, parts of the Mediterranean, as well as the northeastern side of the Indian Ocean
location and risk of tsunami is dependent on
topography, reefs, vegetation
Primary impacts of tsunamis
-Damage to both the landscape and human structures from resulting flooding and erosion
Secondary impacts of tsunamis
- fires from ruptured natural gas lines or flammable chemicals
- water pollution and damaged waste water treatment systems
- disease outbreaks, health impacts, complete environmental contamination
How to minimize the tsunami hazards
- Detection and warning
- For distant tsunamis: can be detected in the open ocean and accurately estimated their arrival time to within a few minutes
- Ex: Hawaii has up to 14 hours to evacuate, minimal time to reach safety
Tsunami warning system
- A network of seismographs to measure submarine movement
- Automated tidal gauges to measure unusual rises and falls of sea level
- A network of sensors connected to floating buoys
- Pressure sensors used to measure wave height (bottom of seabed)
- Waves=1 meter in open ocean, 500 Kl
You can minimize tsunami hazards through structural control and building design
- Build updated and strong homes
- Japanese home
- Fukushima nuclear power station; harbor walls break waters and resist tsunami
- Aceh, Indonesia: nothing left standing but the masque
- Hilo Hawaii: elevated home allows tsunami to pass underneath
Tsunami run up maps
- minimize tsunami hazard
- Need information about elevation of city to predict storm surge
- Determine runup height and level to which water travels inland
- Huntington beach, CA: U.S. pro surf contest (thousands of ppl)
Land use planning, forests and mangroves
- minimize the tsunami hazard
- Healthy mangrove forests helped save lives in the Asia tsunami disaster
- IUCN compared the death toll from two villages in Sri Lanka; two people died in the settlement with dense mangrove and scrub forest, while up to 6,000 died in the village without similar vegetation
healthy ecosystems
act as natural barriers against tsunamis
Three main ways to minimize tsunami hazard
- structural control and building design
- tsunami run up maps
- land use planning-forests and mangroves
Probability Analysis
- The risk of a particular event occurring times the consequences (damage, cost, lives)
- Identify and specify the potential earthquake sources
- Specify relationships that will either attenuate or reduce tsunami waves
- Similar approach to earthquake hazard analysis
- Still being developed
Education is critical for tsunamis
- most people don’t know if a tsunami watch or warning is issued
- In 2005 in Santa Barbara, no mention of size of the possible tsunami, some people drove too far to the top of a nearby mountain pass thousands of feet above sea level
- No plan for people to directly observe the tsunami
Tsunami watch
an earthquake that can cause a tsunami has occurred
Tsunami warning
that a tsunami has been detected and is spreading across the ocean toward their area
Chilean EQ
- tsunami advisory issued for California coast following deadly 8.3 magnitude EQ in Chile
- Sept 17th, 2015
Tsunami warning issued for Hawaii
- after magnitude 7.7 EQ in British Columbia
- October 8, 2012
Typically, all waves in ocean are generated by
wind
wind generated waves
- 5-60 miles per hour (8-100 kilometers/hr)
- wave period: 5-20 seconds apart (low frequency)
- wavelength=300-600 ft apart (100-200 meters)
Tsunami wave
- 500-600 miles per hour (800-965 kilometers/hr) (100x stronger)
- wave period: 10 minutes (600 seconds)-2 hours apart (7,200 seconds)
- wave length=60-300 miles apart (100-500 kilometers apart)
wave period
time between waves
large swells
20 second waves generated by hurricanes
center of hurricane
choppy, low frequency
During a tsunami
- the second and third waves may be larger than the first one, these may be up to an hour apart between waves
- Move to higher ground and stay there until instructed otherwise
Ways to establish a tsunami ready status
- Establish an emergency operation center with 24 hour capability
- Have ways to receive tsunami warnings from the national weather service, Canadian meteorological center, coast guard, or other agencies
- Have workable ways to alert the public
- Preparedness plan with emergency drills
- Promote community awareness and education
Why do you think that prior to the 2004 Indonesian tsunami there was no warning system in the Indian ocean?
-They never had a tsunami of that magnitude
Harry Glicken
- ph.d student observation posts at mount st. helen (1980) with dave Johnston
- Eruption took place, Dave let emergency services know, died at the site
- Harry Glicken became well known, died monitoring Mt. Unzen in Japan
Papua, New Guinea
volcano eruption accompanied by shockwave
Mt. Unzen
- One of 19 active volcanoes in Japan
- Erupted and killed approx. 15,000 people 200 years ago
Violent eruption on June 3, 1991 (Japan)
- 1000s of ash falls by 1993, the king of the ash flow centers’
- 44 people killed, including Harry Glicken, a U.S. volcanologist who escaped death in the May 18, 1980 eruption of Mount St. Helen
The king of the ash flow center
Mt. Unzen
Mt. Unzen, Japan precautions
- attempts to control mud overflow via constructed channel
- not entirely successful
How many volcanic eruptions on earth/yr
1,500 active volcanoes on earth, 50 eruptions per year
Most active volcano countries
Japan, Mexico, Philippines, and Indonesia
Where is most volcanic activity concentrated?
Most activity concentrated along major plate boundaries
U.S. volcanic activity
- Alaska, Hawaii, and pacific NW most active
- 1 to 2 eruptions/year
How and where is magma formed
- From asthenosphere associated with subduction zones
- Forms lava when reaches surface
- Mid-oceanic ridges
Volcanic activity depends on
- Depending on lavas viscosity And amount of dissolved gas content
- Determined by silica content (lava composition) and lava temperature.
Viscosity
liquids resistance to flow
High Silica means
high viscosity
Quiet flow v. violent eruptions
- quiet flow: low viscous basalt flow
- violent explosion: high viscous lava eruption
Four main volcano types
- shield volcano (flat)
- composite or stratovolcano
- volcanic dome
- cinder dome
Two main types of volcanos
Shield and composite (or stratovolcano)=two main types
Shield volcano is built up almost entirely from
- numerous basaltic lava flows
- Low silicon content (not explosive)
- Typically made of basalt
The slope of a shield volcano is
very gentle
Example of shield volcano
Mauna Loa, Hawaii
Composite or stratovolcanoes are known for their
-beautiful cone shape, distinguished by a mixture of explosive activity and lava flows
Classic volcano
composite or stratovolcanoes
Composite or stratovolcanoes are made up of
- rock form: andesite
- intermediate silica content (explosive)
Example of composite volcano
(stratovolcano) Mt. Fuji, Japan’s tallest peak (3.7 km) and one of the three sacred mountains
Volcanic Domes are characterized by
- viscous magma with a relatively high silica content
- dome shaped and highly explosive
- High silica/viscosity
Rock form of volcanic domes
Rhyolite
Example of volcanic dome
-Mt. Lassen, CA: erupted in 1914
Cinder Cones
- relatively small cone-shaped volcanoes formed from tephra (volcanic ash)
- Cone shaped, often with summit crater
- steep sides
Cinder cones have
-low silica/low viscosity
Rock type of cinder cone
Basalt
Cinder cone eruption type
tephra (mostly ash) ejection
Example of Cinder cone
- Paricutin, Michoacan, Mexico
- A fast growing cinder cone volcano and the youngest in Mexico
- also, Springerville, AZ
The tectonic origins of different types of volcanoes helps explain
the chemical differences in their rock types
Volcanism occuring at mid-oceanic ridges
produces basaltic rocks (low si-content-low viscosity)
Shield volcanoes are formed
- above hot spots located below moving lithospheric plates
- Rock type is mostly basalt
Composite volcanoes are formed along
- subduction zones where rising magma mixes with oceanic and continental crust
- (rocks are mostly andesite-intermediate Si content)
Composite volcanoes are common along the
pacific belt
Caldera-forming eruptions
- may be extremely explosive and violent, usually inland from subduction zones.
- Penetrate hi Si continental crust
main rock type in caldera-forming eruptions
Rhyolite
Silica increases
-Basalt->Andesite->Rhyolite
Typical Volcanic Features
- Craters
- Calderas
- Volcanic vents
- Hotsprings & geysers
Craters
- Bowl-shaped depressions at the top of volcanoes
- Formed by explosions or collapse of the upper part of the volcanic cone
- Few kms in diameter
Calderas
- When a large magma chamber is emptied by a volcanic eruption or by subsurface magma movement
- The unsupported rock that forms the roof of the magma chamber collapses to form a large crater
Volcanic Vents
Locations from which lava flows and pyroclastic material is erupted
Volcanic vent components
vent, conduit, and chamber
Example of volcanic vent
Kilauea, Hawaii
Hot springs
- Hydrologic features associated with some volcanic areas
- Groundwater comes into contact with hot rock and discharges at surface as hot or thermal spring
Example of hot spring
Blue lagoon, Iceland
Geysers
- A vent in earth’s surface that periodically ejects a column of hot water and steam
- Groundwater comes into conduit (vent), water heats, forces accumulation to release steam and water
Example of Geyser
- Fly (artificial) geyser, Fly Ranch NV
- Old faithful, Yellowstone National Park
Volcanic Hazards
- Lava flows: from the vent of a crater or along a line of fissure
- Most common and abundant type: basaltic lava low
Basaltic Lava types
- Pahoehoe lava and Aa lava
- both are slow moving
- able to outrun the lava
Pahoehoe lava
less viscous, higher temp, with a smooth ropy surface texture
Aa lava
more viscous and slow moving, lower temp, with a blocky surface texture
Lava Flow example
- Hawaiian Island Lava Flows: 1983-2005
- Kalapana & Kilauea Google Earth
What 3 records did the U.S. break this year
-failure of snow, excess of rain, hottest july, (1 in 1000 floods in SC, excess rain in NC)
Hurricane Patricia Recap
- Strongest Landfalling Pacific Hurricane on Record
- Maximum sustained winds reached an unprecedented 200 mph (320 kph) and its central pressure fell to 879 millibars (along pacific coast of Mexico)
Deaths and damage reported in powerful Afghanistan quake
- 7.5 magnitude earthquake hits south Asia
- Many people in this region live in mud brick buildings prone to collapsing
- The mountainous region and poor infrastructure make assessing the aftermath difficult
- Epicenter of EQ is a rural and sparsely populated area
Where and how did they attempt to control ash flows
- Mt Helgafell, Iceland (1973)
- Hydraulic chilling of lava flows using water cannons
Pyroclastic flow
A fluidized mixture of solid (rock) to semi-solid fragments (volcanic glass and ash) and hot, expanding gases that flows rapidly down the flank of a volcanic edifice.
Associated with explosive volcanic eruptions
Pyroclastic flow
Examples of Pyroclastic
- Mt Pinatubo, Phillippines (1991)
- Dome collapse and pyroclastic flow at Unzen Volcano
Ash Falls
- Cover large area, 100s or 1,000s of km2
- Impacts to crops and trees
- Surface water contamination
- Harm to human health – poisonous gases, smog
- Structural damage to buildings (weight)
- Blocking of solar radiation
- Hazardous for air traffic – volcanic glass
Nuue Ardentes
- (french for Glowing Cloud)
- Up to 200 degrees C and move up to 800 km/hr
- Incinerate everything in their path
Mt Pelée, Martinique (1902)
- 30,000 dead, 2 survivors
- ‘Prisoner of St Pierre’ circus show
- example of Nuee Ardentes
Volcanic Impact Risks
-Poisonous gases
Floating in air
Dissolved in water
Dangerous for health, plants, and animals
Producing smog air (vog), acid rain, and toxic soil
Health effects of vog: breathing problems,
headaches, sore throats, watery eyes
Can release from a dormant volcano (does not have to be active to release toxic gas)
Volcanic gases
-H2o, CO2, CO, SO2, H2s (acid rain, toxic soils)
Lake Nyos, Cameroon (1986)
- Dormant crater lake volcano
- CO2 moved 10 km downslope
- 1700 people dead and 3000 cattle
Vog
- poisonous gases that produce smog air
- Vog health warnings are also issued In Hawaii periodically (So2)
Debris and Mudflows are also known as
-Lahars
Debris and mudflows (Lahars)
- Large volumes of volcanic material become saturated with water-destabilize
- sudden melting of snow caps and glaciers at the top of a volcano
- Rapid downslope flow at the speed of 50 km/h
- Long flowing distance: tens of miles from the volcano
Lahars may trigger
submarine avalanches and tsunamis
Example of a mudflow or lahar
a hot lahar rushes down a river valley in Guatemala near the Santa Maria volcano, 1989
Canary Islands, Atlantic (potential volcanic landslides and tsunamis)
- Six huge landslides and debris avalanches in the past
- Mt. Teide and Canera Caldera off Tenerife
- Worries about potential Atlantic mega-tsunami
- Potentially could affect the east coast
How to forecast volcanic activity
- Seismic Activities: Earthquakes as precursors
- Thermal, magnetic, and hydrologic conditions
Volcanic monitoring and prediction procedures
o Topographic monitoring: tilting and special bulging
o Remote sensing: radar 3-D interferometry
o Geologic history of a volcano
Pakistan floods 2010
- Population has grown from 34 m in 1951 to 170 m in 2010
- Most people live close to the Indus River
- August of 2010, the greatest monsoon rains in decades, caused catastrophic flooding in Pakistan
- Killed about 1,600 people and 20 million people were affected
- 20% of Pakistan was flooded
Historical use of rivers
- Soil, water supply, ease of waste disposal, commerce, transportation
- Need to understand floodplain and its relation to the river
- The pioneers moved west modifying the land: cutting and burning trees, modifying natural drainage
History of Cape Fear River
- Wilmington was a large trading center and getting naval stores which included lumber, tar, and resin was important for early commerce
- Salt, commodities, and important from NY and the West Indies, and had to travel upstream to the states interior
- Critical for economic needs
Streams
small rivers
Streams and rivers are part of the
hydrologic (water) cycle – water runoff makes its way to rivers & streams
River components
- River channel
- Floodplain (flat area next to river which is periodically inundated)
- Network of streams
- Watershed or drainage basin (region drained by single river)
Stream total load
Total amount of sediments
Bed load
Coarse particles moving along the bottom of river channel,
Suspended load
- Accounts for ~90 % of total load and makes river look muddy
- stuff in suspension within the water column gets picked up as its relatively light
Dissolved load
(e.g. Mg, Ca & Na ions)
Sediments in river
- stream total load
- bed load
- suspended load
- dissolved load
Continuity equation components for river
- Q = discharge (e.g. m3/sec)
- W = width of flow
- D = depth of flow
- V = velocity (e.g. m/sec)
Stream velocity
Largely dependent on stream gradient, discharge, and channel shape (erosion vs deposition)
Velocity is dependent on
gradient (slope) of river
Stream Competence
- measuring he maximum size of the sediments transported by a river
- ex: mountains: boulders
Stream capacity
- is the maximum amount of solid load (bed and suspended) a stream can carry
- depends on both the discharge and the velocity
Hjulstrom curve
deposition, transportation and erosion of different particle sizes based on flow velocity
Alluvial plains and deltas
- As rivers enter a coastal plain or water body, they deposit their load due to a reduction in velocity
- distributary channels
Examples of alluvial plains and deltas
-Ex: Tenakee Inlet river delta Alaska, Mississippi river delta, Alluvial fan-death valley
Distributary channels
several channels which distribute sediment
Riverbank erosion or deposition is attributed to
- Change in cross-section properties (width, depth, slope)
- Rock and sediment types and properties (mud, sand, and rock)
- Vegetation
- Land-use change (dams)
Land-use change examples
- effects stream morphology
- deforestation, farming, reforestation
- dams
Braided channels
wide, shallow, gravelly and associated with steep rivers or glaciers
Braided channels require
coarse sediments and high flows
Examples of braided rivers
- Saskatchewan River
- Granada, Spain
Meandering rivers
-Erosion and deposition along meanders formation of: -cut banks -point bars -oxbow lakes
Example of meandering river
-Koyakuk River, Alaska
Flooding or overbank flow
occurs when discharge is greater than channel’s holding capacity
Flooding or overbank flow depends on
- rate & amount of precipitation
- Soil type (e.g. porosity)
- Topography
Flooding or overbank may occur
due to snow melt or dam failure
River flooding
- Stage: The height of the water level in a river at a given location at a given time
- Hydrograph: Graphic representation of a river’s discharge over time
- Lag time: The amount of time between theoccurrence of peak rainfall and the onset of flooding
Upstream, Downstream and Flash Flooding
- Upstream flood: Shorter duration, smaller area
- Downstream flood: Longer duration, greater magnitude, larger area
- Flash flood: High volume of flooding over short duration, short lag time, usually upstream
