6. Earthquakes that shouldn’t happen
1 / 38

INTRAPLATE - PowerPoint PPT Presentation

  • Uploaded on

6. Earthquakes that shouldn’t happen. DIFFUSE BOUNDARY ZONES. INTRAPLATE. NARROW BOUNDARIES. Most earthquakes are on plate boundaries, but some are within plates - intraplate. 1900 -. Almost all large earthquakes in North America are in the western plate boundary zone.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' INTRAPLATE' - amato

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

6. Earthquakes that shouldn’t happen





Most earthquakes are on plate boundaries, but some are within plates - intraplate.

1900 -

Almost all large earthquakes in North America are in the western plate boundary zone.

To see New Madrid, we plot down to magnitude 5, which aren’t very big & do little harm.

To resolve details, plot eastern North America down to magnitude 3.

See New Madrid and other similar eastern earthquake zones.


DD 10.1

Charleston, South Carolina 1886 M ~ 7

Similar to New Madrid 1811-12

Damaged buildings - especially brick & caused about 60 fatalities

Similar sand blows

Recovery took about five years

DD 10.2

Grand Banks, Newfoundland 1933 M 7.3

Caused landslide & tsunami

Broke transatlantic cables

Intensity pattern like 1811-12


At plate boundaries, faults are the boundaries and plate motions provide stresses that cause motion

What about within continental plates?

Granite continents vs basalt oceans

Continental crust is less dense, so continents are higher than ocean basins

Continents float above denser mantle

Continents don’t subduct, unlike oceans

Continents formed earlier in Earth history and can reach ages of billions of years compared to 200 Ma oceans

DD 10.3


Oceanic lithosphere is formed at midocean ridges & destroyed at subduction zones

Continental plates are rifted apart and then collide, but survive

East African Rift

Gulf of Aden, Gulf of California


Southern Europe

Himalaya Zagros

Continental rifting

Young ocean

Ocean-continent convergence

Closing ocean

Stein & Wysession, 2003

Continental collision

DD 10.4

Global Plate TectonicsJurassic to Present Day


L.A. Lawver, M.F. Coffin, I.W.D. Dalziel

L.M. Gahagan, D.A. Campbell, and R.M. Schmitz

2001, University of Texas Institute for Geophysics

February 9, 2001

Activity 6 1 wilson cycle

Activity 6.1: Wilson cycle

When does the North Atlantic rift open?

When does the South Atlantic rift open?

When does India collide with Eurasia?

When does Arabia rift away from Africa?

Some continental rifts fail to split a continent

Leave “failed rift” - long valley of stretched & faulted rock

that gets filled up & buried by sediments


Midcontinent Rift system

Failed to split North America ~1.1 Ga (billion years ago)

Activity 6.2

Why does the MCRS show up so well in gravity & magnetic maps?


Over billions of years, continents retain structures formed by rifting, collisions, failed rifts, basin formation, faulting, etc

Stresses within the plate - from various sources - can reactivate these & cause intraplate earthquakes

S. Marshak

A set of failed rifts, the Reelfoot Rift and Rough Creek Graben, are associated with the New Madrid & Wabash Valley seismic zones

S. Marshak

Activity 6.3: Spot formation of the MCRS and Reeflfoot/Rough creek rifts

Whitmeyer & Karlstrom 2007

Reelfoot rift formed when supercontinent of rodinia broke up

Reelfoot Rift formed when supercontinent of Rodinia broke up Reeflfoot/Rough creek rifts


Meert & Torsvik, 2003