Themes of the Day:

• Hazards, Disasters, and Natural Processes
• Evaluating Hazards
• Human Response to Hazards
• Types of Hazards
• *Break*
• Earthquake Basics
• Strike & Dip
• Faults

Hazards, Disasters, and Natural Processes

• Hazards to Life and Property
• Why are Natural Events Hazardous?
• Magnitude and Frequency
• Death and Damage: How Much?

Evaluating Hazards

• Fundamental Principles Concerning Natural Hazards
  • Hazards are predictable from scientific evaluation.
  • Risk analysis is an important component in understanding impacts resulting from hazardous processes.
  • Hazards are linked.
  • Hazardous events that previously produced disasters are often now producing catastrophes.
  • Consequences of hazards can be minimized.
• Role of History
• Linkages between Hazards
• Disaster Prediction and Warning
  • Identifying Location
  • Probability of Occurrence
  • Precursor Events
  • Forecasting
  • Warning
  • (Action!)
• Risk Assessment
  • Risk Determination
  • Acceptable Risk
  • Problems and Opportunities

Human Response to Hazards

• Reactive Response - Ouch!
• Proactive Response
  • Insurance
  • Evacuation
  • Disaster Preparedness (Planning)
• Artifical Control of Natural Processes

Global Climate and Hazards

Population, Land-Use Change, and Natural Hazards

• Effect of Population Growth on toll from Hazardous Events
• Effect of Land Use Changes

Earthquake Basics

• Focus (or hypocenter) - point of initial breakage - seismic body waves emanate from the focus
• Epicenter - point at surface directly above focus - seismic surface waves emanate from the epicenter
• Fault Scarp - surface breakage on a fault zone

Strike & Dip

• Strike - the intersection of a horizontal plane with a planar feature in a rock (such as sedimentary bedding or metamorphic foliation) - measured in the horizontal plane as the azimuth or bearing of the strike line
• Dip - oriented perpendicular to strike - the directly downhill direction - measured in the vertical plane as the angle from the horizontal down to the dipping plane
• Strike and dip are measured in the field and used to describe the attitude of geologic features on maps

Faults

• Brittle deformation - more common shallow in the crust or as a result of high strain rates
• Joints are fractures that have no offset - "Joints Relieve Stress"
• Fault Types:
  • Strike-slip (transform) faults - vertical fault planes, strike-slip movement, right-lateral and left-lateral senses of movement - example: San Andreas Fault, CA
  • Normal Faults - dipping fault planes, dip-slip movement, hanging wall moves down with respect to the footwall - thinning and extension of the crust - associated with divergent plate boundaries - detachment faults or horst & graben structure
  • Reverse Faults (Thrust Faults)- dipping fault planes, dip-slip movement, hanging wall moves up with respect to the footwall - thickening and compression of the crust - Thrust Faults have shallow dips (< 30^o) - associated with convergent plate boundaries - Example: Keystone Thrust, NV
  • Oblique-slip - some combination of dip-slip and strike-slip - resulting from transtension or transpression - associated with transform plate boundaries

Earthquake Causes

• Earthquakes occur when rocks under stress undergo brittle failure and slide past each other along a fault plane
• Elastic Rebound Theory
• Foreshocks & Aftershocks
• Fault Types and Plate Boundaries
  • Normal Faults - Divergent Plate Boundaries
  • Reverse Faults - Convergent Plate Boundaries
  • Strike-slip Faults - Transform Plate Boundaries
• 90% of earthquakes occur at or near plate boundaries