GSU GEOL 1122K - Study Guide Chapter 8 (15 pages)

Unformatted text preview:

Essentials of Geology 4th edition by Stephen Marshak 2013 W W Norton Company Chapter 8 A Violent Pulse Earthquakes 1 A Violent Pulse Earthquakes 2 Introduction Earth shaking caused by a rapid release of energy Energy moves outward as an expanding sphere of waves This waveform energy can be measured around the globe Earthquakes are common on this planet They occur every day More than a million detectable earthquakes per year Most earthquakes result from tectonic plate motion 3 Introduction Most earthquakes are small Large earthquakes however Destroy buildings and kill people 3 5 million deaths in the last 2 000 years Several hundred per year 4 Introduction Most earthquake damage is due to ground shaking Earthquakes also spawn devastating tsunamis December 26 2004 Indian Ocean tsunami March 11 2011 eastern coast of Japan What Causes Earthquakes Seismicity earthquake activity occurs due to Sudden motion along a newly formed crustal fault Sudden slip along an existing fault A sudden change in mineral structure Movement of magma in a volcano Volcanic eruption Giant landslides Meteorite impacts Nuclear detonations Fault slip is the most PowerPoint slides prepared by Rick Oches Professor of Geology Environmental Sciences Bentley University Waltham Massachusetts common cause 5 1 6 What Causes Earthquakes Hypocenter focus the place were fault slip occurs Usually occurs on a fault surface Movement of magma in a volcano Volcanic eruption Giant landslides Meteorite impacts Nuclear detonations Essentials of Geology 4th edition by Stephen Marshak Fault slip is the most 2013 W W Norton Company common cause Chapter 8 A Violent Pulse Earthquakes 6 What Causes Earthquakes Hypocenter focus the place were fault slip occurs Usually occurs on a fault surface Earthquake waves expand outward from the hypocenter Epicenter land surface right above the hypocenter Maps often portray the location of epicenters 7 Faults in the Crust Faults are crustal breaks where movement occurs Displacement is a measure of movement Fault trace is the ground surface expression of a fault On a sloping fault crustal blocks are classified as Footwall block below the fault Hanging wall block above the fault 8 Faults in the Crust The fault type is based on relative block motion Normal fault The hanging wall moves down relative to the footwall Results from extension pull apart or stretching 9 Faults in the Crust The fault type is based on relative block motion Reverse fault The hanging wall moves up relative to the footwall Results from compression squeezing or shortening The slope dip of fault is steep 10 Faults in the Crust The fault type is based on relative block motion Thrust fault A special kind of reverse fault The slope dip of fault surface is much less steep Common fault type in compressional mountain belts PowerPoint slides prepared by Rick Oches Professor of Geology Environmental Sciences Bentley University Waltham Massachusetts 11 Faults in the Crust The fault type is based on relative