Evening star. [volume] (Washington, D.C.) 1854-1972, 1926-07-04
SCIENCE TO STUDY
TINY EARTHQUAKES
Microtremors to Be Followed
by Means of HighIy-Sen-
Sitive Device.

studying earthquakes III 1dIlloIil id
with a. microscope to learn their
whims and so to help prevent such
damage as that in San Francisco in
1906 and in Santa Barbara in 1925 is
the program inaugurated in the re-
gion of Los Angeles by the Carnegie
Institution and now being introduced
by local business interests around San
Francisco, according to DR.. Bailey
Willis. professor emeritus of geology
at Leland Stanford University and
president of the Seismological Society
of America, who is now in Washing
ton.
Earthquake centers are located in
belts" Prof. Willis says, zone belt sur
rounding the Pacific Ocean and an
other extending across Southern Asia
and the Mediterranean. Still another
belt crosses the West Indies. The
belts are related to zones of growing
mountains, where there are marked
differences in elevation, sometimes be-
tween mountainous regions and low
lands and sometimes between the land
and the bottom Of the sea. These diff
ferences in level. however. are the eff
feet, and not the cause, of earth
quakes, because the forces which pro-
duce the Quakes are those engaged in
pushing up live mountain ranges.
quake survey, we now have maps Of
earthquake regions which for accu-
racy and completeness may be COM
pared with the maps Of the continents
| in the time Of Queen Elizabeth, but
we need much better maps, and to get
them we must have closer surveys.
For that purpose we have need Of a
new type OF instrument or seismom-
eter.
Intricate Instrument Used.
I'm designing this new type, the ex-
| perts of the Carnegie. Institution have
resorted to a pendulum which scarcely
weighs an ounce and is attached to a
tungsten steel wire as fine as spl-
der's web. 1t carries small mirror
| which reflects a pencil of light and the
| latter draws the record on moving
| Photographic film. In size and weight
the instrument Is exceedingly strong
| and yet it offers no large mass by
which an earthquake could destroy 1t,
as is the case with older designs.
1T has thus been made possible to
record a microscopic earthquake and
we might we'll call the operation the
study of earthquakes with micro
scope. These microscopic earthquakes
are called microtremors. They occur
constantly in earthquake regions and
| frequently in other places. as on the
Atlantic Coast. Their frequency and
| intensity is a gauge Of earthquake &C.
| tivity.
when we know more about them,
we shall be able to follow these minute
elastic vibrations very much in the
| same way as the Weather Bureau now
| follows fluctuations Of the barometer.
| We expect that in time we shall be
| able to tell from them the approach
| Of an earthquake Storm and thus
| may come nearer to forecasting
understanding which is now i'm
possible.
Establishing Four Stations.
| with a view to making a local sur
| vey, the Carnegie Institution Is estab-
! fishing four stations in Southern Cal
| ifornia. located at Pasadena, River
| side, La Jolla and probably. Catalina
Island. The range of each station for
microtremors Is about SO miles and OF
| course longer for heavier shocks. The
| four stations will, therefore, cover the
whole Of the coastal region Of South
ern California, and from their records
we shall obtain a good knowledge or
the distribution Of earthquake activ-
! ity. One of the instruments at Pasa-
| dena recorded 200 microtremors in Its
| first IL months Of experimental opera
| ton.
THE example Of the Carnegie In
stitution led to an active campaign
for the installation Of modern seis-
mometers around San Francisco Bay,
and funds have been raised by bust
| ness men and corporations of the cities
| on the bay for that purpose. The
| central station will be located at
Berkeley, at the University Of Cali
| fornia. which will also run subsid-
iary station at the Lick Observatory
on Mt. Hamilton. Stanford University
will take care Of a third, and the Cali
fornia Academy Of Science in Golden
| Gate Park, of fourth. The cost Of
| these instruments, including the nee
essary earthquake-proof shelter, full
| equipment of seismometers and time
recording apparatus, amounts to
| S22, 900. Their maintenance and the
| study of their records is assumed by
the three institutions named
| "It is anticipated that we shall thus
learn what the present earthquake &C.
tiyity Is, and that we shall be able
| to locate it and follow its variation
as II increases toward the next severe
shock.
"The installation of similar groups
Of instruments, not only in other parts
of California but around Boston, New
| York, st. Louis, New Orleans, and
other great centers Of population and
property, is one of the things to
| which business men should give
serious consideration, and toward
| ,,yh;ch THAR contributions would con.