IF YOU'VE SPEN T time at UC San Diego,
you know that when it comes to earthquakes, it’s not a matter of if, but when.
For researchers, however, it’s also a matter
of how—how it will happen and how it will
impact the places where we live and work.
A new study by scientists at Scripps
Institution of Oceanography says that in
addition to “The Big One,” subsequent
aftershocks on separate faults following
a large earthquake could cascade and
lead to mega-earthquakes.
Scripps geophysicist Peter Shearer
and graduate student Wenyuan Fan have
discovered 48 previously unidentified
large aftershocks that occurred on faults
adjacent to the main shock rupture just
after large-magnitude earthquakes.
For instance, off the coast of Indonesia,
a magnitude 7 quake triggered two large
aftershocks over 200 kilometers
(124 miles) away.
These aftershocks, while miles away
from the initial quake, reveal that stress
can be transferred almost instantaneously
by the passing of seismic waves from one
fault to another.
“By studying this type of triggering,
we may be able to forecast hosting faults
for large earthquakes,” says Fan.
Scientists generally believe that most
aftershocks are triggered by stress changes
caused by permanent movement of the fault
and mainly occur near the main rupture
where these changes are largest. The new
findings suggest that aftershocks can also
be triggered by seismic wave transients,
where the locations of the main quake
and the aftershock may not be directly
“Multiple fault system interactions
are not fully considered in seismic hazard
analyses, and this study might motivate
future modeling efforts to account for
these effects,” says Shearer.
Revealing the cracks in
the Earth and our structures.
UNDERSTANDING THE PLANET
BY ANNIE REISEWITZ AND IOANA PATRINGENARU
SHAKE I T UP
Researchers tested a six-story,
lightweight steel-frame building to
see how it would fare during an
earthquake and subsequent fires.