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General Issues > Early Warning

What Explanations Can Be Given for these Mixed Results?

An earthquake hypocenter might possibly lie directly under the city to be protected. In this case, an early warning system simply has no chance of catching appropriate signals in time to generate an early warning.

An early warning system might also fail to be effective when the event originates in an area not sufficiently covered by sensors. Here, a greater number of sensors could help.

Hardware failure (either sensor or transmission) has often been an explanation. Here again, the highly-redundant structure of a super-dense network eliminates such concerns.

Software bugs are another story. In a network with super-dense instrumentation, there is no need for powerful machines to run highly-complex algorithms in order to identify a "real" event from any given station.

This historical overview suggests that we formulate two principles that might enhance the performance of seismic early warning systems in the future:

• avoid highly complex systems—install multiple units with robust technology instead
• apply voting schemes to a highly redundant structure of identical units