Evening star., 1960-06-12
Three Quakes
Shook Chile,
Study Shows
BY RICHARD FRYKLUND
Star Stan Writer

OSCdIl, dIlO OOuIII AIlcIlCt
shuddered. Then another sec.
ton dropped. And a third.
That was the Chilean earth
quake in essence, according tt
United States Geological Sur.
vey scientists who are complet-
ing a preliminary study of the
quake. William D. Carter, 9
USGS mining geologist, just re.
turned from the earthquake
area with the first news oi
what really happened to Chile
Other scientists, including DR.
Pierre Saint Amand, a leading
authority on earthquakes, are
still in the area.
Among Strongest
Their preliminary conclusions
are:
This was one Of the strongest
quakes in hiStory-possibly as
bad as the record-breaker al
Assam, India, in 1852.
1t was caused by a sudden
drop and lateral shift Of the
coast of South Chile.
There were at least three
distinct drops over a period OF
several days as successive
chunks Of coast slid into the
water.
The Chilean quake was one
scene in a drama that has con-
tinued for millions Of years in
the Pacific basin. The San
Francisco quake was another
More will certainly come.
All the edges of the Pacific
basin are earthquake zones. AL
seem to be dropping and per-
haps rotating. When a section
gives way. it drops the coast
several feet into the ocean,
shakes up the land for hun
dredS Of miles around and fire.
quently starts seismic waves on
the ocean which cross and re-
cross the Pacific basin.
Coast Analysed
The coast Of Chile is an i'm
mense cliff, starting from the
top of a coastal range Of noun
tains and going down at some
points five miles, under the sea.
Landward Of the mountains is
a coastal plain Of deep sand
and gravel beds. The plain ends
where the Andes rise along
Chile'S eastern border.
The mountains have broad,
rounded valleys with steep
sides, cut thousands Of years
ago by glaciers.
This is a perfect stage set
ting for a destructive earth
quake.
1t started when several miles
of coast in central Chile
dropped suddenly May 81. The
largest shift of rock occurred
about so miles out to sea and
several hundred miles under
the deep Peru-Chile Trench.
The center of greatest shock
an damage on the surface was
at the city of Valdivia.
The soft floor Of the central
valley carried the shock waves
up and down the center of
Chile. AS the earth heaved,
cities toppled.
New Section Fell
The next day a long section
Of the coast farther south
dropped. The center Of damage
this time was Ancud, about
$50 miles south of Valdivia.
Several days later another Sec
ton fell. The center Of dam
age was Puerto Aysen, 200
miles south of Ancud.
A total of 600 to 1000 miles
of coast slid into the sea in
the series of catastropheS.
There may have been still a
fourth drop farther south, al
most to the Strait of Magellan,
according to seismographs and
newspaper reports. But no
competent scientist has been
able to visit that sparsely in
habited area to see.
Biologists say the coast off
Puerto Aysen dropped about 80
feet downward and seaward
several hundred years ago. It
will take some time to deter
mine whether the shift was
that big this time, but crack
ing and shearing of the ground
there indicate it was quite a
drop.
Coast Sagged
And it was fast. Big trees
near Ancud were snapped of
cleanly at the trunck, appar-
emily by a sudden sideward
shift of the ground holding the
roots.
While the coast sagged and
the central plan undulated, the
high sides Of mountain valleys
tore loose and thundered down
the rounded shute. Some land
slides were two miles wide. They
blocked rivers in the same way
a smaller landslide blocked the
Madison river in Montana last
summer.
Volcanic activity that accom-
panied the quake seems to have
been exaggerated. No new VOL
canoes were created, although
new vents in the old ones we're
opened by the shifting earth,
One quiet volcano, Puyehue,
east Of Valdivia, fumed and
sputtered when a long fissure
was opened on its southwest
flank, but it did not send out
a heavy lava flow as had been
feared.