Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Kashiwazaki-Kariwa Nuclear Power Plant wikipedia , lookup
2009–18 Oklahoma earthquake swarms wikipedia , lookup
April 2015 Nepal earthquake wikipedia , lookup
2009 L'Aquila earthquake wikipedia , lookup
1880 Luzon earthquakes wikipedia , lookup
1570 Ferrara earthquake wikipedia , lookup
Earthquake engineering wikipedia , lookup
1906 San Francisco earthquake wikipedia , lookup
Seismic retrofit wikipedia , lookup
VII. Earthquakes A. B. C. D. E. Introduction Source of seismic energy Propagation of seismic energy Recording earthquakes Magnitude scales San Francisco, 1906 Building design could not withstand accelerations $Millions of damage Thousands of people killed http://news.nationalgeographic.com/news/2003 Geology in the News California, 2003 Two die in 6.5 magnitude Earthquake near San Lois Obispo California Earthquake triggers mudslides San Andreas Fault Earthquake Bam, Iran A Magnitude 6.5 Earthquake hits a stone- and mudhouse city of 100,000 in Iran December 26, 2003 30,000 Dead 30,000 Refugees US sends aid and releases sanctions Relations improved Photos from AP Geological Hazards Related to Earthquakes Volcanoes Landslides Tsunamis Mudslides B: Sources of Seismic Energy Elastic Rebound Buildup of elastic energy during elastic strain Sudden release due to slippage along a fault or brittle rupture Anatomy of an Earthquake Fig. 8.35 Focus: Source of energy Epicenter: Location directly above focus at the surface (ground motion is greatest) Fault Trace: Shows intersection of fault and the surface of the land Fault Scarp: Indicates vertical motion of fault Propagation of Seismic Energy Body Waves travel through the earths interior (crust, mantle, core) P wave: Compression and expansion of rock S Wave: Shearing motion of particles Fig. 8.42 Propagation of a P-Wave Propagation of Seismic Energy Body Waves travel through the earth’s interior (crust, mantle, core) P wave: Compression and expansion of rock S Wave: Shearing motion of particles Surface Waves Propagation of an S-Wave Propagation of Surface Waves Surface Waves travel along the earth’s surface Love Wave: Lateral movement of the surface Rayleigh Wave: Rolling movement of the surface (similar to an ocean wave) Propagation of a Surface Wave Propagation of a Surface Wave Recording Earth Motion Seismograph: An instrument that measures the horizontal or vertical motion of Earth’s surface Seismograms: The plot of the motion Measuring Velocity of Seismic waves Because the P wave travels faster the the S wave The S-P interval increases with distance Time of Earthquake Time of Earthquake Reading a Seismogram Ground motion vs. Time See Fig. 8.44 Each tick mark is 1 minute P-S Time interval indicates distance to epicenter P-S Interval First P wave Arrival First S wave Arrival First Surface wave Time-Distance Relationships See Fig. 8.45 Use P-S interval to determine distance to focus Distance from focus (Kilometers) Seismic Waves and Velocities P-waves a = (k + ¾m)r k: Bulk modulus m: Mod. of rigidity r: Density S-waves b = m/r Body Waves and Surface Waves Locating the Epicenter Triangulation using 3 seismograph stations Depth can be determined with four or more stations Finding the Depth of Earthquakes Using 4 or more seismograph stations Seismicity of the Pacific Rim 1975-1995 Shallow quakes at mid ocean ridges (<33km) and Oceanic trenches Deep quakes over the subduction zone (>70 km) 0 33 70 150 300 500 800 Depth (km) Earthquakes, Plate Interior New Madrid Fault Zone Faults activated by crustal warping Bowling Green Fault Largest Earthquake on the N. American Continent New Madrid Earthquake, 1811 Modified Mercalli Intensity Scale Subjective observations of Damage and Ground motion Is not a quantitative measure Earthquake Intensity Scales Modified Mercalli Scale Subjective observations of Damage and Ground motion Is not a quantitative measure Richter Scale Indicates Ground Motion Amplitude Logarithmic (e.g., 6 is ten times stronger than 5) Does not directly indicate energy or destruction Earthquakes around the World Assessing Risk “Major Quake Likely to Strike San Francisco Bay Region Between 2003 and 2032” Geologic Hazards • Assessing Risks • Avoiding Risks • Preventing Damage • Predicting Impact Seismic Risk Analysis Quake history (statistics) Locations of active faults Competency of surficial materials (soil and rock) Ocean basin source Tsunamis Solomon Islands Earth Quake and Tsunami 4-1-07 Profiling Earth’s Interior Velocities of seismic waves vs depth Fig. 19.19 & 20 Imaging Earth’s Interior P and S waves are refracted (bent) within the earth S waves do not travel through fluids Fig. 9.21