Time progress left to right and from top to bottom, just like
text on a printed page. Each line is 30 minutes long. The
minute marks are visible as diagonal stripes on the upper half
of the record.

The original record was made photographically with a light beam
focused on a piece of photographic paper. When waves from the
1964 earthquake arrived the beam began moving back and forth so
quickly that the photographic paper did not receive enough light
to register the position of the trace. This situation continued
for many hour following the earthquake, which is why the record
above has a white band at the center.

Here is a much larger image of the seismogram. It will take a
while to download because is size is 1.1 MB!