>>> 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.