ISNS 4359
EARTHQUAKES AND VOLCANOES
Spring 2005
The Big Picture - A Synthesis, Comparisons, Contrasts
Steve Bergman, Instructor-
Lecture 22. Earthquakes & Volcanoes Hazards: Mitigation & Prediction
Hazard-a specific, dangerous physical phenomenon or process
Earthquake Hazards (Most vulnerable states in USA-AK, CA, WA, OR, ID, NV, UT, MO, AR, IL)
Direct- Ground Shaking, Fault Displacements, Fissures, Tectonic Uplift/Subsidence
Induced- Tsunami, Landslides, Avalanches, Liquefaction, Compaction, Seiches, Fire
Volcanic Hazards (Most vulnerable states in USA-AK, OR, WA, CA, HI)
Direct- Pyroclastic Flows, Surges, & Falls; Lahars, Debris Avalanches, Landslides, Gas, Ash, Lavas
Induced- Tsunami, Famine & Disease, Fire
Earthquake Prediction (specify Time, Place, & Size [Impact])
Time (long-term->decade, intermediate-yr, short-week/month, immediate-<day); Place (long-range, narrow, exact)
Earthquake Forecast-statistical chances of an EQ based on past activity.
Deterministic-largest EQ likely on a particular fault or in a region in a given time interval (GutenbergRichter Scaling Law-plot log [cumulative number of EQ] vs magnitude).
Probabilistic-likelihood of a given size EQ striking a fault or region within a future time interval.
Long Term Regional Precursors - Historical Record, Seismic gaps, Linear Migration
Short Term Precursors - Ground Tilting, Radon Emanation, Water Well (ground water) changes,
Rock Properties (resistivity, seismic velocity), foreshock activity (however, less than half of M>7
events are preceded by significant foreshocks); Anomalous Animal Behavior (days-seconds: Motoji
Ikeya, 2004. Earthquakes & Animals, from folk legends to science, World Scientific Publ. Singapore, 295pp.).
Some successful predictions have saved thousands of lives-Haicheng-Yingkou China 4 Feb 1975 (many
foreshocks, only 1328 killed with 95% of houses collapsed, compared to M7.8 Tangshan unpredicted EQ on
28July1976 killing >255,000-no foreshocks), Mayor of Perahora Greece evacuated his town after a foreshock of
the 1981 Corinth event (157 buildings collapsed, only 3 killed).
Failed predictions: Lucca, Italy 56,000 evacuated by mayor after small tremor, freed 13,000 hospital beds, fire
brigade mobilized, petrol shortages, traffic jams, nothing followed; mayor sacked. Brian Brady (US Bureau Mines)
predicted M>9 EQ in Lima Peru for 28June1981, based on anomalous EQ in 1974-5 (no EQ in following 20 yrs).
Parkfield CA (M5.5-6.5 in 1857, 1881, 1901, 22, 34, 66; each in same spot on SAF with similar foreshocks; 22 yr
period except 1934) in 1984, USGS forecast 95% probability of M~6 in 1988±5, but no EQ, although 1983 Coalingua
& 1985 Kettleman Hills events 30 km E of the San Andreas may have relieved stresses.
Prediction is currently elusive - much anticipated Parkfield, CA event finally materialized 20 years late.
[In 1984 USGS predicted M5-6 between 1985 & 1993, based on 22 year recurrence interval, previous 120 years].
Volcanic Prediction (specify Time, Place, Size [Impact])
Magma Chamber Mass Change (gravity), Ground Deformation/tilting, Soil Gas (CO2, He, Rn, SO2), Water
Temperature, Volcanic Seismicity, Volcanic Tremor, Magnetic/Electrical Fields; anomalous animal behavior.
Recent Eruptions at Mt. St. Helens, Pinatubo, and many other volcanoes have been successfully predicted;
evacuations have saved many thousands of lives.
Nota Bene <10% of the world's 1300 active volcanoes have been mapped and studied for hazards potential.
Volcanic Earthquakes-High frequency slip (P&S: 5-15 Hz), Low Frequency bubble pressurization (P wave only:
1-5 Hz, tornillo/screw shape) Explosions (air shock), Tremor (continuous, minute-day duration, 1-5 Hz)
Hazard MitigationAnticipatory Response (Avoid Hazard)
Physical Development: Land-Use & Urban Planning, Prevent Collapse-Reduce Damage
Characterization: Determine history/frequency
Prediction & Warning: Preparedness-Insurance-(Intervention)-Evacuation-Refuge Facilities
Emergency Response: Save Lives-Protect Property
Disaster Recovery: Immediate Relief (days), Rehabilitation (months), Reconstruction & Relocation/Improvements
(years-decades)
Early Warning Systems: seismic waves & tsunami much slower than light & electrons; accelerometer/gas shut off valves.
House Preparation-Hire geotech engineer to evaluate-secure house to foundation with bolts, secure shelves, water heater,
plywood sheathing not diagonals
What to do during an EQ? Remain Calm, Action depends on where you are and condition of building: if inside-get under
interior desk table or doorway; if downtown, do not rush outside due to falling debris & glass; if in car-stop in an open area.