Earthquakes, Volcanoes, and a Modern Journey to the Center of the Earth

Michael WysessionProfessor of Geophysics, Dept of Earth and Planetary Sciences

Washington University, St. Louis, Missouri

PLATE

“Plate Tectonics,” The Basic Idea:

Locations of the Major Tectonic “Plates”

A Global Map of Earthquakes Also Shows the Plate Boundaries

Japanese Folklore: Earthquakes caused by giant Namazu.

Following the 1755 Lisbon earthquake on All Saint’s Day, the Spanish Inquisition burned people at the stake to atone for the city’s sins.

The San Andreas Fault

The Global Seismic Hazard Assessment Program (GSHAP), with the support of the International Council of Scientific Unions (ICSU), and endorsed as a demonstration program in the framework of the United Nations International Decade for Natural Disaster Reduction (UN/IDNDR).

More reasonable assessment, based upon actual seismicity

Earthquakes occur where earthquakes occur, and…

Earthquakes occur where seismometers exist

Earthquakes occur where earthquakes occur

Earthquakes occur where seismometers exist

Almost no seismometers!!

The NMFZ is associated with the Reelfoot Rift – a failed rift zone that was active 750 million years ago, as the supercontinent Rodinia began to break up.

The Reelfoot Rift is a region of lower elevation (which is why the Mississippi River flows down through it!).

New Madrid earthquakes

o Historical o Instrumental

Notice all the earthquakes EAST of the NMSZ!

The NMSZ might be finished (for now?). It might be time for a different failed rift to undergo some continental creaking.

Wabash Valley Seismic Zone earthquakes:

The latest - Mw 5.2 on April 18, 2008 (last Friday!)

A DEVASTATING EVENT: THE SUMATRA EARTHQUAKE OF DECEMBER 26, 2004

Burma Microplate Sumatra

Indian Plate

Northward Motion of

India Deforms

the Entire Region

SumatraEarthquake

Sumatra-Andaman Dec 26, 2004 EQ & TsunamiSumatra-Andaman Dec 26, 2004 EQ & Tsunami

Banda Aceh:

Before….

Banda Aceh:

Before….

and After…..

So….could this happen in America?!?

Massive landslides in places like the Canary Islands could cause enormous Atlantic tsunamis!

There have also been Giant Undersea Landslides in the Puerto Rico Trench!!!!

For Large Earthquakes, Seismic Waves Circle the Earth for Months to Years, Making it Ring Like a Gong.

(Earth’s Lowest Note, With a Period of ~54 Minutes, is an E, Twenty Octaves Below Middle E on a Piano.)

Courtesy of J. Tromp

Courtesy of IRIS

Can Seismologists Predict Earthquakes?

(Only one earthquake was ever successfully predicted: 1975 Tangshan, China)

Earthquake Prediction: Animal Behavior?

Earthquake Forecasting: Seismic Gap Hypothesis?

Lack of success reminiscent of New York City “bear gap” hypothesis

USGS Forecast: Parkfield Earthquake in 1987

On Sep. 28, 2004, the Parkfield EQ finally happened!!

Was it is successful prediction???

Courtesy of A. Dziewonski

Seismic Imaging Has Allowed Us to Explore the Interior of Our Planet….

A Medical CT-Scan

Courtesy of S. Zhong

DOWNWELLING UPWELLING

For a copy of this presentation, please email me at:

michael@seismo.wustl.edu

The information can also be found (and more) in the 48-lecture Teaching Company video course “How the Earth Works”