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Earthquakes and seismic history of Florida ( FGS: Information circular 93 )
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Title: Earthquakes and seismic history of Florida ( FGS: Information circular 93 )
Series Title: ( FGS: Information circular 93 )
Physical Description: Book
Creator: Lane, Ed
Publisher: Florida Geological Survey
Publication Date: 1983
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Subjects / Keywords: Earthquakes -- Florida
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Funding: Digitized as a collaborative project with the Florida Geological Survey, Florida Department of Environmental Protection.
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Source Institution: University of Florida
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Table of Contents
    Front Cover
        Page i
    Front Matter
        Page ii
        Page iii
        Page iv
    Table of Contents
        Page v
    Earthquakes and seismic history of Florida
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
    Selected bibliography
        Page 8
    Back Matter
        Page 9
        Page 10
        Copyright
            Copyright
Full Text




STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Elton J. Gissendanner, Executive Director


DIVISION OF RESOURCE MANAGEMENT
Casey J. Gluckman, Director


BUREAU OF GEOLOGY
Charles W. Hendry, Jr., Chief


INFORMATION CIRCULAR NO. 93

EARTHQUAKES AND SEISMIC HISTORY
OF FLORIDA

By
Ed Lane





Published for the
BUREAU OF GEOLOGY
DIVISION OF RESOURCE MANAGEMENT
FLORIDA DEPARTMENT OF NATURAL RESOURCES


TALLAHASSEE
1983


'UNIVERSITY OF FLORIDA LIBRARIES






QU






SCIENCE
LIBRARY





DEPARTMENT
OF
NATURAL RESOURCES


BOB GRAHAM
Governor


GEORGE FIRESTONE
Secretary of State


BILL GUNTER
Treasurer


RALPH D. TURLINGTON
Commissioner of Education


JIM SMITH
Attorney General


GERALD A. LEWIS -
Comptroller

DOYLE CONNER
Commissioner of Agriculture


ELTON J. GISSENDANNER
Executive Director








LETTER OF TRANSMITTAL


BUREAU OF GEOLOGY
TALLAHASSEE
July 30,1983


Governor Bob Graham, Chairman
Florida Department of Natural Resources
Tallahassee, Florida 32301

Dear Governor Graham:

The Bureau of Geology, Division of Resource Management, Depart-
ment of Natural Resources, is publishing as Information Circular No. 93,
"Earthquakes and Seismic History of Florida'," prepared by Ed Lane, a
staff geologist with the Bureau.

This report presents the history of earthquakes felt in Florida and dis-
cusses how they occur and how they are detected and measured. This
aspect of Florida's natural history is of interest to the general public,
government officials, and teachers. This information should help to
allay the fears that arise whenever earthquakes or rumors of earth-
quakes occur.

Respectfully yours,

Charles W. Hendry, Jr., Chief
Bureau of Geology









































Printed for the
Florida Department of Natural Resources
Division of Resource Management
Bureau of Geology

Tallahassee
1983








iv

















CONTENTS
Page
Earthquakes and seismic history of Florida ................................ 1
Selected bibliography ................................................ 8

ILLUSTRATIONS
Figure
1 Cross section of earth showing propagation of seismic waves ........... 2
2 Water level recorder seismogramm" of world's largest earthquake in 1978... 3
3 Water level recorder seismogramm" of 1979 Colombian earthquake ........ 3
4 Water level recorder seismogramm" of the 1964 Good Friday Alaskan
earthquake ..................................................... 4
5 Seismic risk map of Florida ........................................ 6

TABLE
Table
1 List of known earthquakes felt in Florida, from 1727 through 1982 ......... 7














AND
SEISMIC HISTORY OF FLORIDA

Earthquakes in Florida? Not likely-that's true-but their effects
have been felt in the historical past. With respect to earthquakes,
Florida is in a region that is classified as stable, that is, earthquakes are
not probable. However, this is a restless earth and no area is truly stable,
in the strictest sense of the word. While earthquakes can and do occur
in stable areas, they are generally much milder than the catastrophic
ones, such as the Alaskan Good Friday earthquake of 1964.
Scientists and news media report earthquakes with terminology that
is useful for comparative purposes. The more common terms are given
here in bold type, with their definitions. An earthquake is the oscillatory,
and sometimes violent movement of the earth's surface that follows the
release of energy somewhere within the earth's crust. This energy can
be generated by a volcanic eruption, a sudden dislocation or move-
ments of segments of the crust along faults, by manmade explosions,
and even bythe great weight of water impounded behind dams. Usually,
though, most destructive earthquakes are caused by movements of the
crust along a fault.
Faults are zones in the earth's crust where there has been movement,
such as the famous San Andreas fault zone in California. A fault occurs
when internal forces cause rocks in the earth's crust to rupture and
move against one another. These sudden ruptures and grinding move-
ments release the energy that causes the ground-shaking, which we call
an earthquake. Geologists have found that earthquakes tend to concen-
trate and recur along faults, and the fact that a fault zone has recently
experienced an earthquake offers no assurance that the internal crustal
stresses have been relieved enough to prevent another earthquake.
Faults in Florida have been found during the exploratory drilling for oil in
the panhandle. These faults are associated with the deeper parts of the
Apalachicola Embayment and with the Foshee Fault system which
extends northward into the state of Alabama. Some other faults have
been postulated along the eastern seaboard, based on tenuous
evidence.
The location of an earthquake is described by the geographic posi-
tion of its focal depth, as shown on Figure 1. The focal depth of an earth-
quake is the depth below the earth's surface to the region (focus) where
the earthquake's energy originates. The epicenter of an earthquake is
the point on the earth's surface directly above the focus.
The energy released by an earthquake at its focus travels as seismic
waves through the earth and along the surface. The first indication of an
earthquake will often be a sharply felt thud, which signals the arrival of
the seismic waves that travel through the earth. This will be followed by
the ground roll or shaking caused by the seismic waves that travel along






BUREAU OF GEOLOGY


the earth's surface. Waves, similar to ocean waves, have been observed
to travel across the ground in response to the surface seismic waves,
literally flipping people and animals off their feet.


Figure 1. Cross section of earth showing how the release of energy at an
earthquake's focus generates seismic waves, which propagate through
the earth. The point on the earth's surface directly over the focus is
called the epicenter.


Vibrations caused by earthquakes are detected, recorded, and meas-
ured by instruments called seismographs. Seismographs have their
frames securely anchored into bedrock and are very sensitive to earth
movements. The zigzag line recorded by a seismograph, called a seis-
mogram, reflects the variations in movement of the rock beneath the
instrument. From data compiled from seismograms recorded at several
different locations, the time of occurrence, the epicenter, the focal
depth, and estimates of the amount of energy released can be deter-
mined for each earthquake.
A water level recorder installed in a water well can act as a seismo-
graph, because the seismic energy waves cause the water level to fluc-
tuate in the well's casing. As the water level is recorded, a record is
preserved of the earthquake, as on a seismogram. The Florida Bureau of
Geology has such a sensitive and intrumented well; it has recorded
many of the world's major earthquakes. Figures 2 and 3 show the fluctu-
ations of the water level in the Bureau's well for two large earthquakes.
Figure 4 shows the effect the great Alaskan earthquake had on another





REPORT OF INVESTIGATION NO. 93


EARTHQUAKE SHOCK 7



0.45 foot

T


RECORDER TRACE OF
NORMAL WATER LEVEL
CHANGES


TIME --


Figure 2. Largest earthquake in the world during 1978, Richter magni-
tude 7.8, struck November 29 about 300 miles southeast of Mexico City,
causing at least 8 deaths. This earthquake caused the water level to fl uc-
tuate 0.45 foot in the Bureau of Geology's well.


EARTHQUAKE --
SHOCK


0.9 foot

1 ~ i


RECORDER TRACE OF
NORMAL WATER LEVEL
CHANGES


TIME -4


Figure 3. The Colombian earthquake of December 12,1979, Richter mag-
nitude 7.9 killed at least 600 people. It caused the water level to fluctuate
0.9 foot in the Bureau of Geology's well.

well located north of Lake Butler, Union County, Florida.
The severity of an earthquake can be expressed in several ways. The
magnitude of an earthquake, as expressed on the Richter Scale, is a
measure of the amplitude of the seismic waves and is related to the
amount of energy released, an amount that can be estimated from seis-
mograms. Magnitudes on the Richter Scale are expressed as whole
numbers and decimals; for example, the Alaskan earthquake of March
27,1964, was Richter magnitude 8.5. However, this scale is logarithmic,
so that each increase in whole number represents a force 10 times
larger than measured by the previous whole number. For example, a


I __ I






BUREAU OF GEOLOGY


'I U. ~ ~ I


I
OVER 10 FEET, OFF
RECORDER SCALE


RECORDER TRACE OF
NORMAL WATER LEVEL
CHANGES


EARTHQUAKE SHOCK





AFTERSHOCKS




















TIME


Figure 4. The Good Friday earthquake that struck Alaska on March 27,
1964, registered 8.5 on the Rightpr scale, and was the largest instrumen-
tally recorded earthquake everto strike the North American continent. It
caused this water level recorder to go off scale in both directions-a
water level fluctuation of over 10 feet. The major shock and the after-
shocks caused the water level to fluctuate for more than two hours.
Water well located north of Lake Butler, Union County, Florida.






REPORT OF INVESTIGATION NO. 93


recording of 3.0 is 10 times as large as 2.0 and 4.0 is 100 times as large as
2.0, and so on. An earthquake of magnitude 2.0 is the smallest normally
felt by humans, while earthquakes with magnitudes of 6.0 or larger are
considered to be major earthquakes.
The intensity of an earthquake, as expressed by the Modified Mercalli
Scale, written as MM, is much more meaningful to laymen than the
Richter Scale since it is based on actual human observations of earth-
quake effects at specific locations. Modified Mercalli Scale values of
shock intensities are given as Roman numerals and range from MM I to
MM XII; "MM I-not felt except by very few people favorably situated,"
to "MM Xll-damage total, lines of sight disturbed, objects are thrown
in the air." The maximum intensity experienced in the Alaskan earth-
quake of 1964 was MM X; in the San Francisco earthquake of 1906 it was
estimated at MM XI.
Official records and newspaper accounts document the occurrences
of many earthquakes since 1727 whose epicenters were in or near
Florida. These earthquakes are listed in Table 1 with estimates of their
epicentral locations and intensities. Several are grouped together, since
they are aftershocks which commonly occur hours, days, or even weeks
after major shocks. Of the earthquakes felt in Florida, only six are
considered to have had epicenters in Florida, and even some of these
possibly were tremors from earthquakes outside Florida. Most of the
earthquakes felt in Florida had estimated local intensities of MM IV to
MM VI. Generally, a tremor of intensity MM IV is: felt indoors by many,
outdoors by few. May awaken light sleepers. Vibrations similar to the
passing of heavy trucks. Dishes, windows rattle; glassware clinks;
houses may creak. Intensity MM VI is: felt by everyone, indoors and out-
doors. Awakens all sleepers. Frightens many people; creates general
excitement. Persons move unsteadily. Trees shake slightly. Liquids
move strongly. Damage to some buildings. Church bells ring. Windows
break; pictures and books fall; furniture overturns. -
Other natural or man-made phenomena causes rumblings or shaking
of the ground which are sometimes mistaken for earthquakes. Such
things as the sudden collapse of a sinkhole or the energy waves from an
explosion have been mistaken by local residents as earthquakes.
Figure 5 shows zones of estimated risk of damage in Florida. It
should be pointed out that, if it had not been for the effects of the great
1886 earthquake at Charleston, South Carolina, all of Florida probably
would be in Zone 0.








BUREAU OF GEOLOGY


ZONE 0. Areas with no
reasonable expectancy of
earthquake damage.


ZONE 1. Areas that may
have minor damage from
largest expected distant
earthquakes.


PALM BECH


'-. --- -
nowARo
COLLIER
i~


Figure 5. Seismic risk map of Florida. (Modified from Seismic Risk Map
of U. S., in Earthquake Information Bulletin, Nov.-Dec. 1974, U. S.
Geological Survey).


POLK


HENRY






REPORT OF INVESTIGATION NO. 93 7



Table 1. Ust of known earthquakes felt in Florida, from 1727 through
1982, with estimated epicenters and intensities. Compiled from
Campbell (1943) and accounts from local newspapers.
October 29,1727: Unofficial sources reported a severe quake, MM VI, in St. Augustine,
but the original record has not been located. New England had a severe shock about
10:40 anm. on this date, and a quake was reported on the island of Martinique on the
same day
February 6,1780: Pensacola felt a tremor described as "mild."
May 8,1781: Pensacola suffered a "severe" tremor that shook ammunition racks from
barrack walls, levelled houses, but no fatalities.
February 8,1843: Earthquake in West Indies, felt in United States, Intensity unknown.
January 12, 1879- Earthquake felt through north and central Florida bounded by a line
drawn from Fort Myers to Daytona on the south, to a line drawn from Tallahassee to
Savannah on the north, an area of about 25,000 square miles. Intensity MM VI near
Gainesville.
January 22and 23,1880: Earthquake in Cuba of intensity MM VII, about 120 miles east of
Havana. Felt in Florida.
January 27, 1880: Several shocks of Intensity MM VII to MM VIII were felt in Key
West resulting from a disastrous earthquake at Vuelta Abajo, about 80 miles west of
Havana, Cuba.
August 31,1886:The great earthquake in Charleston, South Carolina, MM X. Felt all over
north Florida, with an estimated intensity of MM V-MM VI. Bells rang in St. Augustine,
and severe shocks were felt along the east coast. Quake effects felt in Tampa.
September 1, 3,5,8,9,1886: Jacksonville felt more aftershocks of intensity about MM IV
from the Charleston quake.
November 5,1886: Jacksonville felt another aftershock from the Charleston quake.
June 2, 1893: Jacksonville felt a tremor at 10*07 p.m. Estimated MM IV.
October 31, 1900: U. S. Coast & Geodetic Survey recorded a local shock of MM V at
Jacksonville.
January 23, 1903: Shock of intensity MM VI was felt at Savannah. Effects felt in north
Florida.
June 1Z 12912 Strong shock felt at Savannah. Intensity unknown. Felt in Florida.
June20,1912: Shockof MM V felt at Savannah; probably associated with the above quake
of June 12. Felt in north Florida.
1930 (exact date not known): An earth tremor was felt over a wide area in central Florida
near LaBelle, Fort Myers and Marco Island. Thought to be from an earthquake, but some
persons believed it was tremendous explosions, though no explosions were known to
have been detonated. Estimated intensity at Marco Island was MM V.
November 13,1935: Two short tremors were felt at Palatka in the early morning. The sec-
ond shock was felt at St. Augustine and on nearby Anastasia Island. Estimated .intensity
at Palatkawas MM IV or MM V.
January 19, 1942: Several shocks felt on south coast of Florida, with some shocks felt
near Lake Okeechobee and in the Fort Myers area. Estimated intensity was about MM IV.
January 5,1945: About 10:00 a.m. windows shook violently in the De Land Courthouse,
Vofusia County.
December22,1945:Shockfelt in the Miami Beach-Hollywood areaat 11t25 a.m. Intensity
MM I to MM IlL
November8,1948: A sudden jar, accompanied by sounds like distant explosions, rattled
doors and windows on Captiva Island, west of Fort Myers.
November 18,1952: Windows and doors were rattled by a slight tremorat Quincy, about
20 miles northwest of Tallahassee.
March 26,1953: Two shocks estimated as MM IV were felt in the Orlando vicinity.
October 27, 1973: Shock felt in central east coastal area of Seminole, Volusia, Orange,
and Brevaid counties, at 121 a.m., maximum intensity MM V.







8 BUREAU OF GEOLOGY


December 4, 1975: Shock felt in Daytona and Orlando areas, 6:57 a.m., maximum inten-
sity MM IV.
January 13,1978: Two shocks reported by residents in eastern part of Polk County south
of Haines City. Tremors were about one minute apart and each lasted.about 15 seconds,
shaking doors and rattling windows. The tremors occurred between 4:10 and 4-20 p.m. No
injuries or damages.
November 13,1978: Tremor felt in parts of northwest Florida near Lake City. Seismic sta-
tion at Americus, Georgia, estimated it originated in the Atlantic Ocean.


SELECTED BIBLIOGRAPHY
Campbell, Robert B., 1943. Earthquakes In Florida, Proceedings of the Florida Academy
of Sciences, vol. 6, no. 1, March, pp. 1-4.
Meadows, Paul, 1981. Records of water level recorders, U. S. Geological Survey-Water
Resources Division, Tallahassee, Florida.
Stover, C. W., B. G. Reagor, and S. T. Algermissen, 1979. Seismicity Map of Florida,
U. S. Geological Survey Map MF-1056.
U. S. Geological Survey, Earthquake Information Bulletin, Nov.-Dec. 1974. Seismic Risk
Map of U. S.







8 BUREAU OF GEOLOGY


December 4, 1975: Shock felt in Daytona and Orlando areas, 6:57 a.m., maximum inten-
sity MM IV.
January 13,1978: Two shocks reported by residents in eastern part of Polk County south
of Haines City. Tremors were about one minute apart and each lasted.about 15 seconds,
shaking doors and rattling windows. The tremors occurred between 4:10 and 4-20 p.m. No
injuries or damages.
November 13,1978: Tremor felt in parts of northwest Florida near Lake City. Seismic sta-
tion at Americus, Georgia, estimated it originated in the Atlantic Ocean.


SELECTED BIBLIOGRAPHY
Campbell, Robert B., 1943. Earthquakes In Florida, Proceedings of the Florida Academy
of Sciences, vol. 6, no. 1, March, pp. 1-4.
Meadows, Paul, 1981. Records of water level recorders, U. S. Geological Survey-Water
Resources Division, Tallahassee, Florida.
Stover, C. W., B. G. Reagor, and S. T. Algermissen, 1979. Seismicity Map of Florida,
U. S. Geological Survey Map MF-1056.
U. S. Geological Survey, Earthquake Information Bulletin, Nov.-Dec. 1974. Seismic Risk
Map of U. S.












FLORIDA DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY
C. W. Hendry,-Chief
S : -S.R. Windham, Assistant Chief


Sahdie Ray Secretary -


Richard Seymore, Secretary


OL. AND GAS SECTION


Clarence Babcock
Robert Caughey, GC
Cynthia Gordon, G
Joan Gruber, Secr




Susie Coleman, A
Greg Daugherty, E
Lee Edmiston, En
Bruce Greenwood
Randy Holcomb,
Zoe Kulakowski, (
Jackie Lioyd, Geo


L. C
, Engineer
geologist
geologist
etary


)avid Curry, Administrator
Gwen Manning, Clerk-Typist
Charles Tootle, Engineer
Jean Wehrmeyer, Secretary


RECLAMATION REGULATION
W. Ross McWilliams, Administrator
dmin. Asst. Amber Mahaffey, Secretary
-nvirdn. Super. Jack Merriam, Biologist
gineer Spec. Harry Neel, Geologist
F, Geologist Lou Neuman, Forester
Secretary Joan Ragland, Geologist
Geologist Lee Sherwood, Environ. Super.
logist Wesley Wimmer, Engineer


RECLAMATION RESEARCH
J. Williari Yon, Administrator
Mondell Beach, Environ. Spec.


GEOLOGIC INVESTIGATIONS SECTION


Tm -Walter Schmidt, Administrator
Thomas W. Allen, Research Asst. Kelly Frierson, Library Assistant
Jonathan D. Arthui Research Asst. Ronald Hoenstine, Geologist
Albert Applegate, Geologist Julia Jones, Secretary
E. W. Bishop, Geologist .- Bill Parker, Research Associate
Paulette Bonhd Geologist Thomas Scott, Geologist
Kenneth Campbell, Geologist David Whittington, Research Asst.


TECHNICAL SUPPORT
Ed Lane, Administrator


Mary Ann:Cleveland, Librarian
Jessie Hawkins, Custodial
Justin Hodges, Engineer
Iichard Howard, Sample Prep.
Pauline Hurst: Draftsman


James P. Jones, Draftsman
Earl Maxwell, Statistician
Simmie Murphy, Pressman
Albert Phillips, Engineer
Steve Spencer, Geologist


_I:










FLRD GEOLIOWC( ICA SURflViEWY~


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