Ch04 6slides pp

Ch04 6slides pp - 1 Basic Principles of Earthquake Geology...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 Basic Principles of Earthquake Geology, Seismology GEOL 171 Earthquakes and Natural Disasters Lisbon Earthquakes 1755 Lisbon Earthquakes 1755 • 2- earthquakes in quick succession • 3 rd earthquake a few hours later. • Numerous people in Church • Over 70,000 dead • 90% of the city destroyed Imaginary street scene during Lisbon earthquake. http://nisee.berkeley.edu/kozak/ Morning November 1, 1755 (All Saints Day) Lisbon Earthquakes 1755 Lisbon Earthquakes 1755 Secondary Damage: Fires http://nisee.berkeley.edu/kozak/ Lisbon Earthquakes 1755 Lisbon Earthquakes 1755 Secondary Damage: Sea Waves or Tsunamis http://nisee.berkeley.edu/kozak/ Lisbon Earthquakes 1755 Lisbon Earthquakes 1755 Global Impact – Social and economic Impact http://nisee.berkeley.edu/kozak/ Earthquake Earthquake • An event in which the earth quakes, and vibrations are felt or recorded. • Caused by volcanic activity, meteorite impacts, undersea landslides, explosions of nuclear bombs or most commonly, by movement of the Earth across a fault • Fault : fracture in the Earth across which the two sides move relative to each other • Stresses build up enough to cause rocks to fracture and shift, sending off waves of seismic energy, felt as earthquake 2 Geology and Fault Recognition Steno’s Laws, 1669 (sedimentary rocks) • Law of Original Horizontality • Law of Superposition • Law of Original Continuity Faults and Geologic Mapping • Understanding faults begins with understanding rock relationships, formalized by Steno : – Law of original horizontality : sediments are originally deposited in horizontal layers – Law of superposition : in undeformed sequence of sedimentary rock layers, each layer is younger than the layer beneath it and older than the layer above it Faults and Geologic Mapping Law of original continuity : sediment layers are continuous, ending only against a topographic high, by pinching out from lack of sediment, or by gradational change from one sediment to another • If sedimentary layer ends abruptly, may have been eroded by water action or truncated by fault passing through layer Fault Recognition Fault Recognition Types of Faults • Jointing – brittle lithospheric rocks fracture and crack • Large stress differential on either side of a fracture results in movement: fracture becomes a fault •S trike and dip used to describe location in 3D space of deformed rock layer • Dip : angle of inclination from horizontal of tilted layer • Strike : compass bearing of horizontal line in tilted layer Fault Surface and Rupture • Faults are complex surfaces • Rupture over period • of weeks to months • Foreshocks • Main Shock • Aftershocks • Fault trace • Epicenter and Hypocenter 3...
View Full Document

{[ snackBarMessage ]}

Page1 / 10

Ch04 6slides pp - 1 Basic Principles of Earthquake Geology...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online