Geologic Hazards Geologic Hazards are those Earth processes that are harmful to humans and/or their property. Includes: Earthquakes Volcanic eruptions Floods Landslides and other forms of mass wasting

Effects of Hazards Primary effects Secondary effects Tertiary effects Direct result of the event (lava flow, ground motion, etc). Secondary effects Associated with, but not a direct response to the event (mudslides, tsunamis, famine and disease, etc). Tertiary effects Long term or permanent changes due to the event (change in topography, climate change, habitat loss, etc).

Hazard vs Risk Hazard assessment focuses on characterizing the physical effects of a geologic event. Risk assessment focuses on the extent of damage (loss) anticipated. Assessments must provide the information in a form that can be readily used by community planners and decision makers.

Hazard Assessment Determine what the event would be like if it occurred now. Location and date of past events. Magnitude and frequency of past events.

Risk Assessment Risk is the probability of a loss within a specific area/time due to a hazardous event. Risk assessment combines: Hazard assessment Location of buildings, facilities, roads, etc. Exposure to physical effects of event. Vulnerability - potential for losses.

Earthquake Hazards Primary Effects of Earthquakes Ground motion Faulting and ground rupture

Earthquake Hazards Secondary Effects of Earthquakes: Aftershocks Tsunamis (seismic sea waves) Landslides Liquefaction and compaction Fires/disruption of municipal services

Earthquake damage Dependent upon: Intensity and duration of seismic vibrations Frequency of seismic activity Local surface geology Amplification of seismic waves Population density/distribution Local construction practices Natural resonance Emergency response/community preparation

Natural Resonance Every object has its own natural vibration period. Hardrock resonance is ~0.5 sec Sediments resonance is 1-2 sec Buildings, resonance increases about 0.1 seconds per story, or 0.1 sec for one-story, 0.5 sec for four-story, and 1 to 2 sec for ten to twenty stories.

Forecasting Earthquakes Long-term forecasting Based on knowledge of tectonic cycles and historical earthquake frequency and intensity. Paleoseismicity - dating of prior earthquakes Seismic gaps - locked fault segments Seismic risk mapping - based on nature and intensity of expected seismic events.

Predicting Earthquakes Short-term prediction Based on observations of precursor phenomena Evidence of micro-crack formation Electrical conductivity Water levels Radon and other soil-gas levels Foreshocks Animal behavior

Earthquakes in Ohio Hazard assessment Tectonic setting Proximity to New Madrid Seismic Zone Historical records Frequency - 120 felt since 1776 infrequency of events limits ability to establish frequency Magnitude - 14 caused moderate damage Recent events 1980 Sharpsburg Kentucky M = 5.3 1998 western Pennsylvania M = 5.2

Earthquakes in Ohio Risk assessment Location of people, facilities, etc Preparedness Exposure Construction practices For more information visit the Ohio DNR at: http://www.dnr.state.oh.us/geo_survey/geo_fact/geo_f03.htm