Rock Island Argus. (Rock Island, Ill.) 1893-1920, 1912-03-07
SCIENTIST
HAS QUAKE DATA
Professor Udden of Augustana
College Gathers Some
Interesting Facts.
ON EARTH SHOCK JAN. "a
Finds Area of Forty Thousand Miles,
Including Rock Island,
Affected.

Prof. Anton d. Udden. head of the |
department of natural science at Au- |
gustana, has made a thorough investi- |
CATION of the earthquake which visited |
the northwestern part of Illinois Jan. |
"a last and has compiled some very |
interesting data. In a lecture before
the advanced class in geology he stat
ed that he had sent out about 800 let
tiers to editors Of newspapers in the
territory affected by the quake and
had received information from $50 10
calities.
Using the so-called Rossi-Forel scale,
Professor Udden determined the inten-
sites of the earthquake at different
places. Intensities, according to this
scale, are denoted increasingly by the
numerals from to 10. No. denotes
shock recorded by a single seismo-
graph; No. 2, extremely feeble shock
recorded by several seismographs; No.
3, very feeble shock felt by persons
at rest; No. 4, feeble shock felt by
persons in motion, rafting of dishes;
No. 8, shock of moderate intensity felt
ticles, breaking Of dishes; No. 6, fairly
strong shock with general awakening
of those asleep, ringing of bells, star
! tied persons leaving their dwellings;
No. Z, strong shock, overthrowing of
movable objects, general panic; No.
s, very strong shock. falling of Chin
neys, cracking of walls; No. 9, ex-
tremely strong shock, partial or total
destruction of some buildings; No. 10,
shock of extreme intensity, great dis
aster, ruins, disturbances of strata,
etc.
OBJECTS OvERTHROWN.
According to the map Professor I'd
den has drawn based upon this scale
the intensities varied from one to six.
The earthquake was most severe in
an area between Morris and Aurora,
the intensities being more nearly sew
en- than six. There the shock was
strong enough to cause movable OBJ
jects to be overthrown, bells to ring
and visible agitation of trees. While
the principal epicenter was in this
area, there appeared to be "a second
airy epicenter in and about Dixon
whose intensity was five. The two
epicenters show that there must have
been two distinct shocks, one of
greater intensity preceded or followed
by one of less severity.
Intensity four is shown by line
drawn from Milwaukee to Madison
and then down to Bloomington and
then up towards Lake Michigan. This
line passes over near the tri-cities
According to the scale the shock felt
here was recorded as being a feeble
} shock" felt by persons in motion, rat
= Ting of dishes, disturbance of nova
5 bic objects.
Observations upon the direction o.
motion of the earthquake were report
ed from four different localities, Chi
y, cago. Milwaukee, Elgin and Rock Is
land, the lines of direction converginl
I towards the region of greatest dis
h turbance.
: The area sensibly affected by thi
: earthquake was about 10000 square
g miles in extent. The time of occur
L ence was variously stated as bein.
> from 1915 to 1875 a. m, while thu
reports on duration ranged from on
second TO three minutes.
: 1909 QUAKE MOST SEVERE
In making a comparison of thi
earthquake with the one which oc
CURED on May 26, 1909, Professor I'd
den found that the one In 1909 was o
greater severity. The area affecte,
by both was found to be substantial.
the same and that the isoseismals o
each spread out from a nearly com
mon center. Professor Udden state
that the coincidence of these tw
earthquakes could hardly be regards
as matter Of chance and that it wa
probable that the shocks were direct
ly connected with a gradual readjus-
ment OF the same strata.
Professor Udden recently delivere
lecture on this earthquake at
meeting of the Illinois State Academ
Of Science held at Bloomington, an
the data which he has gathered wi
appear in the official record of thei
nrOceedinps