>>> RECENT EARTHQUAKES AND AFTERSHOCKS HAVE DEVASTATED THE
ISLAND OF PUERTO RICO.
BUT WHAT'S CAUSING THEM, AND WHAT DOES THE FUTURE HOLD?
I SAT DOWN WITH JACK LOVELESS, SMITH COLLEGE ASSOCIATE
PROFESSOR OF GEOSCIENCES, TO FIND OUT MORE.
>> PUERTO RICO IS IN A TECTONICALLY ACTIVE AREA WHERE
SOME OF THE WORLD'S TECTONIC PLATES ARE MEETING.
SO EVERY EARTHQUAKE IN THE WORLD HAPPENS ON A FAULT AND THE
BOUNDARY BETWEEN TECTONIC PLATES ARE THE WORLD'S LARGEST FAULTS
WHERE EARTHQUAKES ARE GOING TO HAPPEN MOST COMMONLY.
PUERTO RICO IS IN A PRETTY COMPLICATED PLACE WHERE THE
NORTH AMERICAN PLATE IS INTERACTING WITH THE CARIBBEAN
TECTONIC PLATE.
AND SO EVERY ONCE IN A WHILE YOU'RE GOING TO HAVE RELEASE OF
ENERGY THAT'S WHAT AN EARTHQUAKE ACTUALLY IS.
THE ENERGY GETS STORED UP AS A RESULT OF THESE TECTONIC PLATES
INTERACTING WITH EACH OTHER AND THEN EVENTUALLY GETS RELEASED.
>> IN TERMS OF THE PATTERN OF THE WAY THE EARTHQUAKES ARE
HAPPENING AS I UNDERSTAND IT'S A LITTLE BIT DIFFERENT, WE MIGHT
TYPICALLY EXPECT A LARGE EARTHQUAKE THEN SERIES OF AFTER
SHOCKS.
BUT THAT ISN'T EXACTLY WHAT'S BEEN HAPPENING IN PUERTO RICO,
RIGHT?
>> RIGHT.
IT ALL STARTED AROUND LATEST OF DECEMBER, I THINK DECEMBER
29th WITH MAGNITUDE 4.7 IT STARTED A WHOLE SEQUENCE OF
EVENTS WHICH OF COURSE HAS CULMINATED IN THE 6.4 AND OWN
AFTER SHOCK SEQUENCE.
AGAIN, NONE OF THESE EARTHQUAKES IS NECESSARILY UNEXPECTED ON ITS
OWN GIVEN THE TECTONIC ACTIVITY OF THE AREA.
WHAT HAS BEEN INTERESTING IS THE FACT THAT WE NOW SEE THAT THERE
WAS WHAT WE CALL A FOUR SHOCK SEQUENCE BEFORE THAT MAGNITUDE
6.4 HOOPS.
>> WHAT DOES THAT MEAN, A FOUR-SHOCK SEQUENCE?
>> SIMILAR TO AN AFTER SHOCK IN THAT REALLY MAYBE WE COULD JUST
THINK OF IT AS NOMENCLATURE THAT IS A FOUR SHOCK, WE CAN ONLY
CALL EARTHQUAKE A FOUR SHOCK ONCE A LARGER EARTHQUAKE HAPPENS
RELATIVELY CLOSE BY BOTH IN SPACE AND TIME.
THE SAME WAY THAT AFTER A MAJOR EARTHQUAKE WE OFTEN SEE AN AFTER
SHOCK SEQUENCE THAT IS A SERIES OF SMALLER EARTHQUAKES THAT
OCCUR IN THE DAYS TO WEEKS TO EVEN MONTHS OR YEARS FOLLOWING
THAT EVENT.
>> SO IN TERMS OF WHEN YOU HEAR MORE THAN 900, SINCE DECEMBER
31st, IS THIS JUST SOMETHING THAT'S NOT COMMONLY REPORTED AND
HAS BEEN GOING ON RIGHT ALONG OR IS THIS SOMETHING NEW AND
DIFFERENT HAPPENING IN PUERTO RICO?
>> WELL, TRULY IN TERMS OF THE NUMBER THAT HAD BEEN HAPPENING,
THOSE WOULD ALL FALL UNDER CATEGORY OF AFTER SHOCKS.
MANY OF THOSE EARTHQUAKES ARE GOING TO BE TOO SMALL TO BE FELT
EVEN IN THE IMMEDIATE VICINITY WHERE THEY'RE OCCURRING.
THERE HAVE BEEN SEVERAL NOTICEABLE AFTER SHOCKS IN ABOUT
MAGNITUDE FIVE RANGE.
THOSE HAVE POTENTIAL TO BE WIDELY FELT AND SOMETIMES HAVE
ADDITIONAL DAMAGE.
AGAIN IN TERMS OF THE RAW NUMBERS, THIS IS AN EXPECTED
AFTER SHOCK SEQUENCE FOLLOWING THAT LARGEST MAGNITUDE 6.4.
>> PERHAPS JUST COMPOUNDED THAT PORT REKEY IS STILL STRUGGLING
TO RECOVER FROM HURRICANE MARIA HAS LOTS OF INFRASTRUCTURE
CHALLENGES AS A RESULT OF THAT.
NOW YOU ADD THIS TO THAT JUST COMPOUNDING THE SITUATION.
>> EXACTLY.
I THINK THE VERY WEAK ELECTRICAL GRID THAT HAS BEEN ESSENTIALLY
UNDER REPAIR SINCE OCCURRENCE OF THOSE HURRICANES WAS ALL THE
MORE FRAGILE THERE FOR SUSCEPTIBLE TO A LOT OF DAMAGE
WITH THIS EARTHQUAKE.
>> I WAS LOOKING AT SOME OF THE U.S. GEOLOGICAL SURVEYS
INFORMATION AND THEY TRACK OBVIOUSLY EARTHQUAKES ACROSS THE
WORLD.
WHEN I LOOKED FOR PUERTO RICO THREE TOTAL IN 2019 THAT WERE
CONSIDERED SIGNIFICANT, WHICH IS A LARGER NUMBER EARTHQUAKE.
AND WHEN WE LOOK AT 2020 SO FAR WE'VE ALREADY HAD THREE WHAT'S
CONSIDERED SIGNIFICANT EARTHQUAKES BY USGst A 6.4, A
5.8 AND 5.6.
IN TERMS MUCH THE MAGNITUDE THAT WE HAVE SEEN SO FAR THIS YEAR
COMPARED TO LAST YEAR, IS THAT UNUSUAL OR KIND OF MORE OF THE
SAME FOR WHAT WE EXPECT OF THE REGION?
>> I THINK WITH EARTHQUAKES ANYWHERE IN THE WORLD WE DON'T
NECESSARILY HAVE AN EXPECTATION THAT THEY WILL OCCUR WITH ANY
GIVEN RATE IN A GIVEN YEAR.
WE CAN TALK ABOUT GLOBAL AVERAGES OR EVEN AVERAGES.
AVERAGE RATES OF OCCURRENCE EVEN WITHIN A PARTICULAR REGION.
BUT EVERY ONCE IN A WHILE THERE IS ANOMALOUS EARTHQUAKE,
PARTICULARLY STRONG RELEASE OF ENERGY.
OFTENTIMES THE RELEASE OF THIS ENERGY MAY TAKE YEARS TO
DECADES, EVEN CENTURIES TO ACCUMULATE TO A LEVEL WHERE IT
THEN NEEDS TO BE RELEASED.
AND WE DON'T HAVE WAY OF KNOWING EXACTLY WHEN THAT WILL HAPPEN OR
IN OTHER WORDS, IN WHICH YEAR A PARTICULARLY STRONG EARTHQUAKE
WILL HAPPEN.
>> IN THAT REGARD IT'S A RELATIVELY INEXACT SCIENCE
WITHIN THIS AREA OF STUDY.
>> RIGHT.
EARTHQUAKES ARE SO FAR THEY ARE UNPREDICTABLE AND WE DON'T HAVE
LOT OF INFORMATION ABOUT ANY PARTICULAR PATTERNS THAT MAY
LEAD US TO BELIEVE AN EARTHQUAKE IS GOING TO HAPPEN.
IT'S A LITTLE BIT DIFFERENT WHEN WE TALK ABOUT THIGHS AFTER
SHOCKS, THE U.S. GEOLOGICAL SURVEY WILL POST VARIOUS AFTER
SHOCK FORECASTS FOR THE NEXT WEEK OR SO GIVEN THEIR
STATISTICAL EXPECTATION OF THE TYPES OF EARTHQUAKES THAT MAY
OCCUR.
>> THOSE FORECASTS ARE THEY SORT OF SIMILAR IN NATURE, STICK WITH
ME HERE FOR A MINUTE, SIMILAR IN NATURE TO WEATHER FORECAST WHERE
IT'S KIND OF OUR SUSPICION BUT REALLY WE KNOW THE WEATHER
FORECAST CHANGES QUITE OFTEN VERY QUICKLY.
IS IT SIMILAR WITH THAT TYPE OF FORECASTING FOR THE USGS?
>> TO SOME EXTENT.
PRIMARILY IT'S BASED ON STATISTICAL COLLECTION OF WHEN
AND WHERE EARTHQUAKES HAVE HAPPENED.
FORECAST, THE USGS AFTER SHOCK FORECASTS CURRENTLY SAY THAT
IT'S MOST LIKELY THAT WE'LL HAVE SOME CONTINUED SMALLER MAGNITUDE
EARTHQUAKES IN THE NEXT WEEK OR SO.
ALTHOUGH THERE IS A VERY SMALL OUTSIDE CHANCE THAT EVEN LARGER
EARTHQUAKE COULD BE TRIGGERED BY THIS EVENT.
AGAIN, WE'RE TALKING ABOUT VERY SMALL PROBABILITIES OF THESE --
THAT PARTICULAR OCCURRENCE.
BUT IT'S NOT OUT OF THE REALM OF POSSIBILITY.
>> I THINK I READ 3% CHANCE WHEN YOU TALK ABOUT SMALL PROBABILITY
JUST TO QUANTIFY FOR FOLKS.
IN TERMS OF WHERE WE GO FROM HERE, WHAT WILL YOU BE WATCHING
AND LISTENING FOR AROUND THIS ISSUE?
>> WELL, IT WILL BE INTERESTING TO CONTINUE TO WATCH THE PATTERN
OF AFTER SHOCKS THAT HAPPEN IN THE NEXT WEEKS.
ACTUALLY SEE HOW LONG THAT SEQUENCE LASTS OVERALL.
IT MIGHT ALSO BE INTERESTING TO SEE IF ANY OTHER EARTHQUAKES IN
OTHER PARTS OF PUERTO RICO, WHETHER IT'S OFF THE NORTH COAST
AS OPPOSED TO OFF THE SOUTH COAST AS THIS EARTHQUAKE WAS.
WHETHER EARTHQUAKES IN SLIGHTLY DIFFERENT LOCATION ALSO OCCUR IN
THE NEXT COUPLE OF WEEKS TO MONTHS.
>> I WAS PREEDING?
WHERE THAT THE TECTONIC PLATES THAT PUERTO RICO IS SITUATED ON
ARE SIMILAR TO THE PACIFIC RIM IN NATURE IS THAT CORRECT?
DO WE KNOW IF THERE'S SIMILAR ACTIVITY HAPPENING THERE, CAN IT
BE COMPARED OR JUST COMPLETELY INACCURATE THING TO THINK ABOUT
COMPARING?
>> NO, I THINK WE CAN THINK ABOUT ANY PAIR OF TECTONIC
PLATES WHERE THEY MEET, THAT IS A PLACE WHERE EARTHQUAKES ARE
GOING TO BE MOST LIKELY TO OCCUR.
THE TYPE OF ACTUAL MOTION THAT HAPPENS AROUND PUERTO RICO IS
ACTUALLY A LITTLE BIT STRANGE, IT IS DIFFERENT FROM WHAT IS
HAPPENING FOR EXAMPLE ON THE WEST COAST OF THE UNITED STATES.
IN THAT CASE WE HAVE WHAT WE COULD THINK OF AS PURELY
HORIZONTAL MOTION PARALLEL TO THE SURFACE OF THE EARTH.
WHERE AS IN PUERTO RICO WE ACTUALLY HAVE ONE PLATE, NORTH
AMERICAN PLATE DIVING UNDERNEATH THE ISLAND OF PUERTO RICO.
SO THERE'S SOME DIFFERENCES IN TERMS OF THE DETAILS OF HOW
THESE TECTONIC PLATES ARE MOVING IN RELATION TO EACH OTHER.
BUT THERE ARE CERTAINLY SOME SIM PLAYERS IN THAT WE HAVE ACTIVE
PLATE TECH NONE I CAN BOUNDARIES BOTH IN PUERTO RICO AND ALONG
THE WEST COAST OF THE U.S.