Earthquakes Class Final Study Guide

What Are the Seven steps to earthquake safety?

1. Secure your space

2. Identify safe spots (under sturdy desk, etc.)

3. Organize disaster supplies

4. minimize financial hardship (organize important docs. / bolt house down)

5. Drop, Cover, Hold on

6. Improve safety

7. reconnect and restore

What are potential fall and fling hazards in a home?

1. Heavy and top-heavy items (fall hazards)

2. Items on shelves and walls (fling hazards)

3. Debris and secondary hazards

What are potential items to put in an emergency kit?

Food, water, safety + light, communication tools, shelter/clothing, medical/personal docs, tools/equipment, pet food/meds, financial docs

What should you do if your inside during an earthquake?

1. Drop, Cover, Hold On

2. If no shelter, get down near an interior wall

3. don't stand in doorways or run outside

4. move away from any hazards

5. if in bed, turn over and cover head with pillow

6. high-rise building, stay away from windows and do not use the elevator

7. If you are cooking, turn off the stove first if possible.

What should you do if your outside during an earthquake?

1. Drop to the ground and crawl toward an open space if you can.

2.Stay away from building exteriors, overhead power lines, trees, light posts, and signs

3. If you are near the shore, or any large body of water (like a large lake), and you feel strong or long-lasting earthquake shaking, or the water suddenly draws back from the beach, tsunami waves may arrive within minutes. go immediately to higher ground or inland away

What should you do if your driving during an earthquake?

1. Do not stop on or under overpasses, bridges, or in tunnels.

2. Safely pull over to the side of the road and set the brake.

3. Do not stop under or near electrical power lines, light posts, trees, or signs, as these may fall.

4. Stay in the car until the shaking is over.

What do you do after an earthquake?

1. Evacuate Only If Necessary

2. Help the Injured and Prevent Shock

3. Check for Hazards and Prevent Further Damage

4. Communicate and Stay Informed

For how many days should your kit allow you to be self sufficient?

at least 3 to 5 days (after hurricane katrina they suggested 5 days to a week)

How much water per person should an emergency kit contain?

One gallon per person per day

What are critical components of an emergency kit?

Water, non perishable food, first aid supplies, medications, flashlights (batteries), tools, fire extinguisher, care items, radio, out-of-area contact info, personal documents and financial items

Why are these components important?

because basic services (such as water, electricity, and gas) may be disrupted for an extended period, potentially up to three weeks, and emergency responders will be overwhelmed. To ensure survival and safety, households must be prepared to be self-sufficient for at least three to five days

What is plate tectonics theory?

a theory developed more than 60 years ago to explain the large scale movements of the lithosphere, it was based around the evidence of sea-floor spreading and ocean topography and palaeomagnetism

Why does the plate tectonic theory matter?

Unifies geology → explains earthquakes, volcanoes, mountains, sea-floor spreading.

What are some early clues for the plate tectonic theory?

- 1620s Bacon: Africa-South America fit.

- 1912 Wegener: Continental Drift (fossils, rock types, coastline fit).Problem: No mechanism → rejected.

What did Wegener propose about "pangea"?

Wegener proposed all continents were once one supercontinent: Pangaea.

Why was wegener rejected?

He couldn't explain how continents move; scientists preferred land bridges/sinking continents.

Evidence Revolution (1960s-70s):

New tech after WWII provided proof for moving plates.

Tectonic Plate theory: Evidence 1: Earthquake Patterns

WWSSN maps showed quakes occur in narrow global belts → outlines plate boundaries.

Tectonic Plate theory: Evidence 2: Ocean Bathymetry

Sea-floor mapping revealed mid-ocean ridges and deep trenches → continents not fixed.

Tectonic Plate theory: Evidence 3: Magnetic Stripes

Symmetrical magnetic bands on ocean floor → sea-floor spreading → new crust forms at ridges.

Tectonic Plate theory: Evidence 4: Hotspot Tracks

Chains like Hawaii form as plates move over fixed mantle plumes → proves plate motion direction & speed.

How many modern plate tectonics are there?

Lithosphere = ~14 major plates moving continuously.

What are divergent boundaries?

Plates move apart → mid-ocean ridges, normal faults.

What are convergent boundaries?

Plates collide → subduction or mountain building → reverse faults.

What are transform boundaries?

Plates slide past each other → strike-slip faults (e.g., San Andreas).

What Drives Plate Motion?

Mantle convection + Earth's internal heat.

What were Flaws and Missing Pieces in the Continental Drift Hypothesis?

1. Lack of a Driving Mechanism (The Core Flaw)

2. Imperfect Fits: Skeptics noted that the coastlines didn't match perfectly

3. Ambiguity in Geological Data (whether rock formations were the same across continental boundaries)

What were flawed alternative explanations for the contential drift hypothesis?

1. Subsided Continents: A prevalent belief was that continents were once connected by land masses that later sank as the Earth cooled and contracted

2. Missing Land Bridges: The fossil record similarities were explained by the hypothesis that ancient land bridges connected the continents but later subsided

What were flaws in Early Modern Earthquake Safety Theory?

1. Assumption of strain release

2. Construction misconception

What is the strain release myth?

- Old belief: Once a fault ruptured, all strain was released → area was "safe" to build (e.g., 1950s Bodega Head nuclear plant idea).

- Reality: Plate tectonics = constant motion → stress always rebuilds → future quakes guaranteed.

What is the construction misconception?

- Early engineers thought heavy brick/steel (URM) buildings were earthquake-safe.

- Reality: URM is extremely dangerous in earthquakes.

What is a hotspot?

the surface expression of a stationary, deep-seated source of heat within the Earth's interior, called a mantle plume, which generates volcanism away from typical plate boundaries

How does a hotspot volcano form?

1. Mantle Plume Origin: A mantle plume, which is a column of hot, buoyant material upwelling from deep within the Earth's mantle, acts as a stationary, fixed source of heat beneath the Earth's surface.

2. Magma Generation: The intense heat from this fixed mantle plume causes melting in the overlying rigid tectonic plate (the lithosphere), generating magma.

3. Active Volcano Formation: This magma rises through the plate and erupts onto the surface, forming an active volcano.

4. Plate Motion: The tectonic plate (either oceanic or continental) moves continuously across the top of the stationary mantle plume.

5. Chain Creation: As the tectonic plate carries the newly formed volcano away from the plume's heat source, that volcano dies out. Simultaneously, the plume generates new magma beneath the crust now positioned directly overhead, forming a new active volcano, thus creating an age-progressive chain.

Can hotspots inform us about plate motion? Why or why not?

1. Yes, hotspots can inform us about plate motion, specifically the absolute plate motion—the movement of a tectonic plate relative to the Earth's deep interior.

2. By analyzing the linear pattern and the ages of the volcanoes along a hotspot track (such as the Hawaiian Island chain), scientists can determine the direction and speed at which the overriding tectonic plate has moved over geological time

What are some examples of hotspots worldwide?

Hawaii, Galapagos, Easter, Macdonald, Yellowstone Caldera (supervolcano), Newberry Track

Are volcanoes related to specific tectonic environments?

volcanoes are strongly related to specific tectonic environments, particularly the boundaries where tectonic plates interact. The distribution of most volcanoes worldwide aligns closely with the lines of earthquake activity, which mark the boundaries of the Earth's lithospheric plates, leading to the designation of the "Ring of Fire" around the Pacific Ocean.

In what tectonic environment do the most destructive earthquakes occur?

The most destructive earthquakes occur primarily in convergent plate boundaries, specifically within subduction zones, where tectonic plates are colliding.

What is a fault?

a fracture in rock with movement across it and/or a surface or plane within the Earth's crust where blocks of rock move relative to one another in response to immense

What is a locked fault?

a fault in the crust that won't move due to frictional resistance

What is a creeping fault?

A fault that moves continuously, slowly releasing the tectonic stress through aseismic creep

What are hybrid faults?

Most active faults, such as the Hayward Fault, display hybrid behavior, meaning they are neither completely locked nor fully creeping

What is association of faults with respective plate boundaries?

The type of movement or deformation at a plate boundary determines the specific type of faulting that occurs there.

What is a strike in relation to faults?

horizontal orientation of the fault.

What it is: Orientation of a fault plane relative to North.

How measured: Angle between horizontal line on the fault and geographic north (clockwise from N).

Example:

0° → north-south

90° → east-west

What is a dip in relation to faults?

angle it slopes downward into the Earth.

What it is: Angle the fault plane slopes into the Earth.

How measured: Downward from horizontal (0° = flat, 90° = vertical).

Example: San Andreas dips ~90° (near-vertical).

How Strike & Dip Describe Fault Motion

- Why they matter: Strike + dip + rake = full 3-D description of earthquake motion.

- Dip-Slip Motion (movement along dip):

Normal faults: Block moves down dip → extension/divergent boundaries.

Reverse/thrust faults: Block moves up dip → compression/convergent boundaries.

- Strike-Slip Motion (movement along strike):

Motion parallel to strike.

Common at transform boundaries.

Fault planes usually near-vertical.

Remote Sensing & Mechanism Determination for strike and dip:

How scientists detect it:

- Use P-wave first motions to infer compression vs dilation.

- Build a moment tensor ("beach ball") showing fault type & orientation.

- Reveals strike, dip, and tectonic setting anywhere an earthquake occurs.

How has the Hayward Fault moved in the past?

its characterized by both gradual, continuous slippage (creep) and sudden, significant ruptures (earthquakes) over geological and historical timescales.

What kind of fault is the hayward fault?

Hybrid fault

How is the hayward fault moving today?

its present-day motion is a combination of two behaviors: slow, continuous creep (aseismic slip) and strain accumulation (locked portions)

How do we measure fault motion?

by integrating geological evidence, which reveals long-term movement, with modern high-precision technologies that capture short-term, continuous, and co-seismic (earthquake-related) movement.

How much of the Pacific-North America plate motion is accommodated on the Hayward Fault?

the Hayward Fault accounts for 20% of the total Pacific-North America plate motion (10 mm/yr out of 50 mm/yr)

What prompted the parkfield experiment?

1. repeating earthquakes (series of m 6 quakes)

2. recurrence rate (fairly uniform avg recurrence interval between events)

3. The prediction ( they forecast that the next Parkfield earthquake would occur in January 1988 ± 5 years.)

Goals of the parkfield experiment?

The primary objective was to observe the earthquake process directly, specifically to identify any precursory signals—an observable sign that occurs days or hours before the main rupture.

What was the instrumentation on the parkfield experiment?

- Seismometers (weak-motion and strong-motion accelerometers) to record subtle microseismicity and strong shaking.

- Creepmeters (simple wires strung across the fault) and laser ranging (a precursor to GPS) to measure minute deformation and fault creep (slow slip).

- Strainmeters installed in boreholes to measure changes in rock stress.

- Magnetometers to detect changes in the Earth's magnetic field.

What was the significance of the parkfield experiment for earthquake prediction?

- It was one of the most ambitious earthquake prediction attempts ever undertaken, aiming to validate the idea that a repeatable seismic cycle exists and that reliable precursors can be identified.

- it was expected to provide the foundational data necessary to create a physical model capable of predicting the exact time and location of earthquakes

What was the result of the park field experiment?

- prediction failure

- no precursory signals (non that are reliable)

- fault variability

- overall it was a wakeup call that prediction is not possible

What is the Ring of Fire?

a volcanically and seismically volatile swath of the Pacific that encircles the ocean basin, running from New Zealand up through Indonesia and Japan, across the ocean to Alaska, and down the west coast of the Americas to Chile.

Clues that revealed Cascadia as a major threat:

- Anatomy mismatch: It sits in the Ring of Fire + has Cascade volcanoes → clear subduction, yet no big quakes recorded.

- Ghost forests: Dead coastal trees showing sudden land drop ~1700.

- Tsunami sand layers: Soil evidence of major subsidence followed by a massive tsunami.

- Orphan tsunami (Japan, 1700): A huge wave with no local quake—timing matched Cascadia.

- Locked fault: GPS/geology showed the CSZ is stuck and building dangerous strain.

What is the Tectonic situation creating earthquakes in the Pacific Northwest?

- The tectonic situation creating earthquakes in the Pacific Northwest (PNW) is characterized by a major convergent plate boundary known as the Cascadia Subduction Zone (CSZ).

- Two major tectonic units in said collision: Juan de Fuca Plate and the North American Plate

- This area sits within the seismically and volcanically active Pacific Ring of Fire and possesses the exact geological features that predict enormous seismic events.

When was the last major earthquake on the Hayward Fault?

Magnitude 6.8 earthquake in 1868

What is regional probability of a major earthquake?

72% probability (or likelihood) one earthquake of magnitude 6.7 or greater will strike somewhere in the San Francisco Bay region before 2043

What is the hayward fault probability?

a 33% chance of a magnitude 6.7 or greater earthquake occurring on the Hayward or Rodgers Creek Fault system by 2043

What is the recurrence interval of the hayward fault?

roughly every 150 years, plus or minus 60 year

Consequences of a Major Earthquake (haywired scenario)

- Casualties (800 deaths, 18,000 nonfatal)

- Displacement (77,000 households, 152,000 with utility outages included, half a milllion displaced)

- Economic Loss (110 billion, 82 in property damage, 30 in fires)

- Building performance (unusable for 10 months)

- rescue needs ( 2,500 from collapsed buildings, 22,000 trapped in stalled elevators)

- utility disruption ( water service lost for 6 weeks, other utility up to 6 moths)

What are the natural hazards associated with a major event?

ground shaking, fault offset, liquefaction, land slides, aftershocks

HayWired Scenario (What / Who / Why)

- What: A realistic M7.0 earthquake scenario on the Hayward Fault created to model cascading impacts (aftershocks, fires, infrastructure + digital outages).

- Who: Developed by the USGS with the HayWired Coalition (50+ agencies: ABAG, Bay Area cities, PG&E, BART, water districts, universities).

- Why: To guide preparedness and risk-reduction by showing what a plausible major Hayward Fault quake would look like—helping policymakers and residents strengthen resilience before the inevitable event.

Where Does the Fault Run on Campus?

The Hayward Fault cuts through the eastern part of the campus. It is recognized as running directly beneath the playing field of the California Memorial Stadium.

How were buildings on campus were built or retrofitted for safety?

- Barrows Hall received "bookends"—additional jacketing of reinforced concrete added to the ends of the building.

- The Residence Halls (like Unit 1) received exterior steel concentrically braced frames (x-braces) to prevent structural swaying and collapse.

- Latimer and Hildebrand Halls (Chemistry buildings) received external concrete exoskeletons and internal unbonded braces, respectively, to resist shear forces.

How does the fault interact with the stadium?

- The fault passes directly beneath the field, subjecting the structure to persistent tectonic stress and creep damage.

- The fault creep split the exterior wall in Section KK, where a gap of up to 50 centimeters (nearly 20 inches) developed over decades and is still visible today.

What are the motions on the hayward fault per year?

- Plate Tectonic Share: The fault accommodates a long-term slip rate of approximately 10 millimeters per year (1 cm/yr)

- Aseismic Creep: released slowly through creep at a rate of approximately 4 millimeters per year (4 mm/yr).

- Strain Accumulation: Because the long-term rate (10 mm/yr) is greater than the creep rate (4 mm/yr), about 6 millimeters per year of strain is accumulating on locked segments of the fault

How Founder's Rock Reached Its Current Position?

Hypothesis: the right-lateral strike-slip movement of the Hayward Fault carried the rock to its current position on campus, transporting it over 10 miles northwest from the Leona Quarry in Oakland, where similar Jurassic-period rhyolite is found.

What is an earthquake source mechanism?

the physical process describing the geometry and direction of slip on the fault that generated an earthquake. It details how the movement of rock blocks relative to one another releases the energy that propagates outward as seismic waves.

What is elastic rebound theory?

Elastic Rebound Theory explains how earthquakes occur through the buildup and sudden release of stress along a fault.

what are the key points/ processes of elastic rebound theory?

- Stress Accumulation: As tectonic plates move, stress builds up along a locked fault.

- Elastic Deformation: The fault is stuck by friction, so the rocks bend and store elastic energy.

- Rupture & Rebound: When stress exceeds friction, the fault suddenly slips, releasing energy as seismic waves and the rocks snap back to their original shape.

Normal Fault: Tectonic environment, Mechanism Type, Moment tensor

- TE = Normal FaultDivergent / Extensional (Plates pull apart)

- Mech.T= Dip-Slip (movement down the dip angle of the fault)

- Moment T= White in the center, black on the edges

Reverse (thrust) Fault: Tectonic environment, Mechanism Type, Moment tensor

- TE = Convergent / Compressional (Plates push together)

- Mech.T= Dip-Slip (movement up and over)

- Moment T= Black in the center, white on the outside

Strike-slip Fault: Tectonic environment, Mechanism Type, Moment tensor

- TE = Transform / Translational (Plates slide past each other)

- Mech.T= Strike-Slip (horizontal movement along the strike of the fault)

- Moment T=Four quadrant cross pattern

What is a focus (hypocenter)?

The exact point underground where the earthquake rupture first begins

What is an epicenter?

The geographic point on the Earth's surface directly above the focus

What is a rupture?

The sudden breaking of a rock mass along a fault plane as the accumulated mechanical stress overcomes the rock's internal strength

What is the rupture area?

- The total surface area of the fault plane (length times width) that slips during an earthquake.

- The overall magnitude of the earthquake scales directly with this area and the amount of slip

Can Aftershocks Help Map Rupture Extent?

Yes, aftershocks are a critical tool for mapping the extent of the rupture area

What is a P-wave (Primary/Pressure Wave)?

A body wave through earths interior. Push-pull motion (compression and rarefaction) where rock particles move parallel to the direction of wave propagation.

Speed of P-wave relative to others?

Fastest seismic wave, traveling at about 6.5 kilometers per second in the crust

What is S-Wave (Secondary/Shear Wave)?

(travel through earths interior) Side-to-side motion (shear) where rock particles move perpendicular to the direction of wave propagation

Speed of S-wave relative to others?

Travels about half the speed of P-waves, or roughly 3.5 kilometers per second in the crust

What is a Love wave and how does it move?

(surface wave along earths surface) Side-to-side motion in the horizontal plane & Slower than S-waves, but slightly faster than Rayleigh waves

What is a Rayleigh wave and how does it move?

(surface wave along earths surface) Circular (retrograde) particle motion in a vertical plane & Slowest seismic wave

Arrival Order by Wave Speed

1. P-waves

2. S-waves

3. Surface waves (Love and Rayleigh waves arrive closely together)

Where do body waves travel?

Body Waves (P-waves and S-waves)

Where do surface waves travel?

Surface waves propagate only along the surface of the Earth

What are is the crust of the earth?

This is the thin outermost shell of the Earth, which is typically brittle and where most shallow earthquakes occur

What is the mantle of the earth?

The Mantle lies beneath the crust and encompasses the vast majority of the planet's volume. It is solid rock, but it behaves like a highly viscous fluid over geological timescales, driving plate tectonic motion through convection The uppermost mantle, along with the crust, forms the rigid lithosphere.

What is the core of the earth?

The deep interior of the Earth contains the core, which has two distinct parts:

- Outer Core: This layer is liquid Scientists know this because S-waves, which require solid material to travel, do not pass through the outer core

- Inner Core: This innermost sanctum of the Earth is solid

How do scientists study Earth's interior?

Scientists utilize the physics of seismic waves generated by earthquakes to remotely study and image the Earth's interior, a method known as seismic tomography. This approach allows researchers to identify the structure and composition of the layers deep beneath the surface, revealing active geological features like subducting plates and mantle plumes.

(when referring to seismic body waves) Hot Rock =

Slower Velocity

(when referring to seismic body waves) Cold Rock =

Faster Velocity

What were key findings along the western US when studying the earths interior?

1. The Juan de Fuca Subducting Slab (Cascadia)

2. Mantle Plumes and Volcanic Tracks (yellowstone plume, slab interactions, newberry track)

What is the Juan de Fuca Subducting Slab?

a dense oceanic plate that is currently subducting (slipping beneath) the less dense North American Plate. This boundary is known as the Cascadia Subduction Zone (CSZ). The slab is generally characterized by high seismic velocity and is causing accumulating strain that will be released in a megathrust earthquake.

What is the yellowstone plume?

a mantle plume, meaning it is a source of hot, buoyant material upwelling from the deep mantle toward the surface with low siesmic velocity and stationary, creating the yellowstone age-progressive track.