principles and applications of microearthquake networks

3.2. Record A‘eepirzg 49
mation. In fact, since most people have a short memory span, we cannot
assimilate more than about l@ bits (or 50 pages) of new information at any
given time. This simple analysis suggests that for any given scientific
observation, we should collect less than l(Y3 bitdyear of raw data in order
not to exceed the capabilities of our present computers. We must also
reduce our results to units of the order of 10” bits each so that we can
comprehend them. For the USGS Central California Microearthquake
Network, we have reached the present computer capabilities in processing
the raw data. However, advances in computer technology are rapid,
and we should be able to process the volume of our raw data by using, for
example, microprocessors in parallel operation. On the other hand, our
human limitations make it difficult for us to assimilate any order of magnitude
increase of new results. Even if the relevant information is present
in the raw data, it is not clear whether we are able to extract it concisely in
order to understand the earthquake-generating process. The problem is
human limitations and not the computers.
3.2. Record Keeping
Record keeping is a procedure to implement data processing goals. It
includes collecting, storing, and cataloging all the information associated
with the operation of a microearthquake network. By “all information”
we mean level 0-level 5 data, which were described in Section 3.1, Although
the need for record keeping is self-evident, many microearthquake
network operators fail to pay enough attention to this task and ultimately
suffer the consequences. It is very tempting to believe that one will remember
the necessary information and to take shortcuts in record keeping.
However, experience shows that unless the information is entered
carefully and immediately on a permanent record, it will soon be forgotten
or lost. For temporary microearthquake networks, it is critical to keep
good records because these networks are often deployed and operated
under unfavorable conditions. For permanent microearthquake networks,
it is not too difficult to devise a record keeping procedure. However, it is
more difficult to maintain it over a long period of time, especially with
turnover of staff. Rather than describe all the details, we will mention a
few typical problems that are often overlooked.
One should begin record keeping as soon as the first station of a microearthquake
network is installed in the field. The station location should
be marked on a large-scale map, such 2s a 1 : 24,000 topographic sheet.
The position of the station should be surveyed or at least be fixed with
respect to several known landmarks using a compass. One test for the