>>> EARLIER THIS MONTH,
CALIFORNIA WAS ROCKED BY A
POWERFUL EARTHQUAKE THAT
MEASURED MAGNITUDE 7.1, THE
BIGGEST QUAKE TO HIT THE STATE
IN 20 YEARS.
IT'S SUBSEQUENTLY EXPERIENCED
FURTHER QUAKES AND SHOCKS IN THE
AFTERMATH.
WHY THE HIGH LEVEL OF ACTIVITY
RECENTLY, AND WHAT'S THE HISTORY
OF EARTHQUAKE ACTIVITY IN THIS
REGION?
I SAT DOWN WITH STEVEN DUNN, A
PROFESSOR AT HOLYOKE COLLEGE FOR
ANSWERS.
>> WHAT THEY ARE HAVING IS
NORMAL IN A LONG TIME SPAN OF
WHAT'S TYPICAL.
THE RIDGECREST EARTHQUAKES ARE
NOTABLE IN A FEW REGARDS.
THEY ARE A LITTLE ACTIVE FAULT
ZONE NEAR THE MOJAVE, AND JULY
4th, WHEN THE FIRST ONE
OCCURRED, WHICH WAS, I THINK, A
6.4 MAGNITUDE, AND EVERYONE
WOULD HAVE ASSUMED THAT THERE
WOULD BE MANY AFTERSHOCKS
BECAUSE THERE'S ALWAYS LARGE
NUMBER OF AFTERSLOBBINGS AFTER A
SIZABLE QUAKE, AND THEN THE NEXT
DAY, JULY 5th, THERE WAS A
LARGER EARTHQUAKE, WHICH WAS NOT
NORMALLY EXPECTED, SO THEN WE
LOOKED BACK AT THE JULY 4th
EARTHQUAKE AND CALLED THAT A
FOUR SHOCK OR A PRECURSOR TO A
LARGER ONE.
THAT'S NOT NORMAL.
TYPICALLY, WHEN YOU HAVE A
SIZABLE EARTHQUAKE, IT'S NOT
PROCEEDED BY PARTICULAR
RECOGNIZABLE ACTIVITY, BUT IN
THIS CASE, IT WAS.
I SHOULDN'T MAKE IT SOUND LIKE
THAT'S TERRIBLY RARE, BUT IT IS
CERTAINLY NOT THE NORMAL WAY,
AND THEN SINCE THE 7.1, THERE'S
BEEN LITERALLY THOUSANDS OF
FOLLOWING EARTHQUAKES ALL OF
SMALL MAGNITUDE, 4 AND LESS, AND
THAT'S VERY TYPICAL.
THAT'S THE CAY WAY EARTHQUAKES .
>> THOUSANDS?
THAT'S NORMAL FOR THAT KIND OF
ACTIVITY?
>> IT IS.
IT IS.
AND THE LARGER THE EARTHQUAKE,
THE MAIN EVENT, THE LARGER IT
IS, THE MORE YOU CAN EXPECT
SIGNIFICANT NUMBERS OF
AFTERSHOCKS AND THE LARGER THE
AFTERSHOCKS WILL BE, SO IN A
REALLY LARGE EARTHQUAKE, YOU CAN
EXPECT THAT THERE WILL BE MORE
AND SOME OF THEM WILL BE
SIZABLE, POTENTIALLY DAMAGING.
SO WHENEVER YOU HAVE AN
EARTHQUAKE, ESPECIALLY A LARGE
ONE, AUTHORITIES WILL WARN
PEOPLE TO STAY AWAY FROM
STRUCTURES THAT LOOK UNSAFE,
FOLLOW UP EARTHQUAKES CAN BE
SIGNIFICANT, BUT IT'S NOT
TYPICAL THAT YOU WOULD SEE A
FOLLOWING EARTHQUAKE THAT'S
LARGER THAN WHAT --
>> RIGHT.
>> THAN A LARGE EARTHQUAKE THAT
HAPPENED PREVIOUSLY.
>> WHEN YOU LOOK AT THIS
HISTORICALLY, SO AT 7.1 WAS THE
GREATSER
GREATER ONE ON JULY 5th,
LARGEST SINCE THE EARLY 1990s,
AND HISTORICALLY, IF YOU CAN
BRING US UP TO DATE WHAT TO
EXPECT LOOKING BACK THROUGH
HISTORY AT THE SIZE OF THE
EARTHQUAKES.
>> WELL, ANYTHING IN THE RANGE
OF 7 OR HIGHER IS A NOTEWORTHY
EARTHQUAKE.
ONCE YOU'RE BELOW AROUND 5, YOU
WOULD NOT EXPECT THERE TO BE
THE LARGE EARTHQUAKES MAGNITUDE
7 AND LARGER, ON A GLOBAL SCALE,
YOU COULD FIGURE THAT IT WOULD
BE ABOUT 2 PER YEAR, SOME PLACE
ON THE PLANET, THAT THERE WOULD
BE TWO REALLY LARGE ONES.
MAYBE MORE LIKE APPROACHING AN
8, SAY, MAGNITUDE ON THE SCALE,
AND SO IN CALIFORNIA ALONE, YOU
MIGHT EXPECT THERE TO BE ONE A
CENTURY, MAYBE A COUPLE A
CENTURY OF 7.0, AND MAYBE THERE
WOULD BE AT LEAST A COUPLE EVERY
HUNDRED YEARS, MAYBE A FEW.
IT'S LIKE THE LAW OF ARCHES.
AV.
YOU DON'T KNOW WHEN OR HOW MANY.
YOU COULD HAVE A CLUSTER OF FIVE
OR SIX IN A FEW DECADES.
THAT'S NOT VERY LIKELY, BUT IT
COULD HAPPEN, OR YOU COULD
ACTUALLY GO A WHOLE CENTURY
WITHOUT HAVING A SIGNIFICANT
SIZABLE EVENT.
THE ONE THAT HAPPENED IN RIDGE
CREST IS -- I DON'T WANT TO SAY
IT'S OF NO CONCERN.
ANY BIG EARTHQUAKE IS OF
CONCERN, BUT THE ONES ALONG THE
SAN ANDREAS, IN PARTICULAR IN
THE REGIONS OF LARGE POPULATIONS
LIKE LANGUAGE AND THE ENTIRE BAY
AREA, THAT'S WHERE MOST OF THE
CONCERN WOULD BE IN CALIFORNIA.
>> AND WHEN YOU LOOK AT THE EAST
COAST, YOU KNOW, THIS IS NOT
SOMETHING THAT WE'RE TYPICALLY
USED TO, NOT A LOT OF HEADLINES
ABOUT IT, BUT IT'S HAPPENED
HERE.
TELL US A LITTLE BIT ABOUT, I
BELIEVE, WE WERE TALKING ABOUT
BEFORE THE ONE IN 2011.
>> RIGHT.
THERE WAS A PRETTY GOOD
EARTHQUAKE IN VIRGINIA.
MY MEMORY IS SAYING 5.8.
IT WAS A PRETTY GOOD SIZED
EARTHQUAKE, AND IT DAMAGED THE
WASHINGTON MONUMENT, WHICH HAD
TO BE CLOSED FOR A COUPLE YEARS
FOR REPAIRS.
IT WAS FELT THROUGHOUT NEW YORK
CITY AND BOSTON.
PEOPLE SCRAMBLED OUT OF
BUILDINGS BECAUSE TALL BUILDINGS
WERE SHAKING.
AND THAT DID QUITE A BIT OF
DAMAGE, AND THAT'S NOT EVEN THAT
LARGE OF AN EARTHQUAKE.
WHEN YOU HAVE LARGE POPULATION
CENTERS AND, PARTICULARLY, HERE
IN THE NORTHEAST AND ANYWHERE IN
THE EAST, THE CONTINUE CONTINENT
IS NOT AS BROKE BROKEN UP AND
SHATTERED BY FAULTING AS
CALIFORNIA IS.
SO WHEN AN EARTHQUAKE HAPPENS
HERE, THE ENERGY IS TRANSMITTED
MUCH FURTHER AND IS FELT WITH A
HARDER SORT OF JOLT, AND SO THAT
EARTHQUAKE IN VIRGINIA WAS FELT
ALL ALONG THE EASTERN SEABOARD
ENTIRELY.
>> AND WHEN YOU THINK OF THAT,
UP TO BOSTON, AND I REMEMBER
WESTERN MASS AS WELL.
>> UH-HUH.
>> THERE WERE REPORTS ABOUT
THAT.
>> IT'S ALSO INTERESTING HERE IN
MASSACHUSETTS, THERE WAS A
REALLY LARGE EARTHQUAKE OFF OF
CAPE ANN BACK IN THE 1700s.
>> OH.
>> 250 YEARS AGO.
THAT WAS FELT -- IT DID DAMAGE
ALL THE WAY TO NEW HAVEN, WHICH
IS AN EXAMPLE OF HOW WHEN A
LARGE EARTHQUAKE HAPPENS IN THE
NORTHEAST, THE -- YOU CAN FEEL
IT, THE SHAKING FOR MUCH LONGER
DISTANCE.
WE ALSO HAVE EVENTS IN WHAT'S
CALLED THE NEW MADRID FAULT IN
SOUTHEAST MISSOURI THAT HAD FOUR
7.5 MAGNITUDE.
WE HAVE TO ESTIMATE BECAUSE THEY
ARE HISTORIC, AND WE DIDN'T HAVE
THE RICHTOR SCALE, BUT IN 1811
AND 1812, OVER TWO YEARS, THERE
WAS FOUR 75.s.5 LOCATION IN
MISSOURI, WHICH IS NOW CLOSE TO
MEMPHIS, TENNESSEE AND OTHER
CITIES.
LOOK AT A HAZARD MAP THAT THE
U.S. GEOLOGICAL SURVEY MAINTAINS
WHERE EARTHQUAKE DANGERS ARE IN
THE U.S., YOU SEE A LARGE AREA
OF CONCERN IN THE CENTER OF THAT
PART OF THE U.S., OVER HERE ON
THE EAST COAST AND THE EAST
COAST NEAR CHARLOTTE.
THERE WAS -- OR CHARLESTON, I
SHOULD SAY, CHARLESTON, SOUTH
CAROLINA, THERE WAS A MAJOR
EARTHQUAKE IN THE 1880s.
YOU HAD THE CAPE ANN EARTHQUAKE
HERE OFF THE COAST OF
MASSACHUSETTS.
YOU HAVE THESE NEW MADRID
EARTHQUAKES IN MISSOURI.
WE ARE NOT FAR REMOVED FROM
POTENTIAL EARTHQUAKE DAMAGE AND
HAZARD.
HOWEVER, THE CHANCES OF THEM
HAPPENING IN ANY GIVEN YEAR ARE
INCREDIBLY LOW WHEREAS IN PLACES
IN CALIFORNIA, THE CHANCES ARE
MUCH, MUCH HIGHER, SO COULD AN
EARTHQUAKE HAPPEN HERE CAUSING
SIGNIFICANT DAMAGE, LOSS OF
LIFE, ECT.?
YES.
IN FACT, IT'S LIKELY THAT IT
WILL, BUT WHEN AND WHERE, WE
HAVE NO IDEA, AND THE LIKELIHOOD
IN ANY GIVEN, EVEN DECADE, IS
VERY, VERY SMALL.
