Weston Observatory

Weston Observatory

Weston Observatory is a geophysical research laboratory of the Department of Earth and Environmental Sciences at Boston College. The Observatory is located in Weston, Massachusetts, about 10 miles west of BC’s Chestnut Hill campus.

Magnitude 9.0Japan

March 11, 2011

How many of you have felt an earthquake?

Which state has the most earthquakes?

(A) California(B) Alaska(C) Missouri(D) Massachusetts

35. Massachusetts 2

Magnitude of 3.5 and greater

What’s the biggest earthquake ever recorded?

(A) Japan, 2011(B) Alaska, 1964(C) Missouri, 1811(D) Chile, 1960

M 9.0M 9.2M 7.5M 9.5

Largest Earthquakes Ever Recorded

1. Chile, 1960 Magnitude 9.5

3. Sumatra, 2004 Magnitude 9.1

2. Alaska, 1964 Magnitude 9.2 4. Japan, 2011

Magnitude 9.0

5. Kamchatka, 1952 Magnitude 9.0

Magnitude 9.0Near East Coast of Honshu, Japan

Magnitude 6.5 – Bali Sea

Magnitude 6.5 - Japan Aftershock

Where do most earthquakes occur?(A) Australia(B) Around the edges of the Atlantic Ocean(C) Around the edges of the Pacific Ocean(D) Antarctica

Earthquakes

Plate Tectonics

Earthquakes correlated with:

* Mid-Ocean Ridges

* Fracture Zones

* Ocean Trenches

1980-2001 (NEIC, M≥5)

NEIC: 01/01/73-12/03/11, M≥5

Mega-Earthquakes: M≥9

Ring of Fire!

Plate Tectonics

Who invented the magnitude scale?

JohnEbel

CharlesRichter

BenoGutenberg

AlanKafka

(A) (B)

(C) (D)

How different is the rate of earthquakes in the Eastern U.S. vs. in California?Each year California has about ____ times the number of earthquakes that the Eastern U.S. has.

(A) 20 (B) 1000 (C) 5 (D) 300

Magnitude 3.5 and Greater, 1974-2003

EUS States: 264

California: 4895 (19 times as many earthquakes as EUS)

Where is the closest plate boundary to Boston?(A) California(B) Mid-Atlantic Ridge(C) Caribbean-North American plate boundary (D) Pacific-North American plate boundary

Plate Tectonics

Where was the largest known earthquake east of the Rockies?

(A) Florida(B) Quebec(C) Missouri(D) Massachusetts

New Madrid, MO: 1811-1812 Charlevoix, Quebec: 1663

Estimated magnitudes each about 7.5From: Ebel (2011)From: Hough et al. (2000)

Where was the largest known earthquake in New England?

(A) Off the coast of southern CT(B) Off the coast of Cape Ann, MA(C) Central VT(D) Southern ME

* MLg 6.2, M 5.9

Cape Ann, MAEarthquake

November 18, 1755

Magnitude 5.9-6.2*

From: Ebel (2006)

VIVII

V

IV

VII

Woodcut illustration showing damage to Boston, MA, during the Cape Ann earthquake of November 18, 1755. Shaking was strongest northeast of Boston. The earthquake caused considerable damage in Boston, knocking down or damaging as many as 1,600 chimneys and collapsing brick walls of several buildings. Image from National Information Service for Earthquake Engineering, University of California, Berkeley.

Eastern United StatesNortheastern United States

Weston Observatory1/1/1975 - 10/11/2011

1700-2011, Magnitude 5.0-7.4USGS

Which of these cities has experienced a damaging earthquake since Europeans settled in North America?

(A) Boston(B) New York City(C) Washington, DC(D) All of the above

New York City August 10, 1884

From Stover and Coffman (1993)

Magnitude 5.2

At about what magnitude level does damage begin to occur?

(A) 2.0

(B) 4.0

(C) 5.0

(D) 7.0

What kinds of buildings are most hazardous in an earthquake?

(A)

(B) (C)

(D)

From: www.iris.edu

Rule of Thumb:

Building period approximately equals number of stories divided by 10.

Building Height Natural Period

1 story 0.1 seconds

2 story 0.2 seconds

5 story 0.5 seconds

10 story 1.0 seconds

20 story 2.0 seconds

30 story 3.0 seconds

50 story 5.0 seconds

SlowerShaking

What should you do if you felt strong earthquake shaking:

• Right now?• If you are in bed?• If you are eating in Lyons?• If you are outside in the

quad?