Hi All,

I found this particular statement puzzling, so perhaps EQF can help me/us understand the statement better:

"Forecasting efforts have now in my opinion reached the point where for some earthquakes at least, after being sent advisories or warnings like that one, government officials might only need to periodically check for reports of fresh cracks in building foundations etc. in some area. Things like that might then serve as indicators that some expected earthquake could be about to occur."

What confuses me in this statement is the conclusion from fresh cracks in buildings prior to an earthquake which would be forecasted for the area in question. If a person inspected a building and found fresh cracks most likely these cracks would be attributed to ground movement which would be in the form of slippage or ground settlement, but not associated with precursory seismic activity.

Aseismic slip, though it occurs in some places on the planet is not an event which occurs with such frequency that one would always attribute this experience to a precursor of a large quake. Most often with aseismic slip only the slip itself occurs, but no quake follows the slip.

This was one of the matters that was viewed in Parkfield for instance. A group of Japanese students were visiting and noticed small fissures in the road where the bus had stopped. Upon later inspection it was noted at a water drain pipe had also moved from its location. Within a few days portable seismic instruments were brought to the site for monitoring, however, no quake of any moderate to large occurred.

A great portion of California has adobe soil and thus cracks in homes and settlement are common occurrences. Using these, therefore, as precursory phenomena is not a valid method.

So, how can we understand what these building cracks might mean upon inspection? There are so many other types of phenomena which are far more obvious, such as sudden water well increase or decrease, increased geyser activity, or a change in geyser behavior, earthquake clustering, or swarms of earthquakes, large solar flares or large quakes which may result in far field earthquakes.

I am at a loss to understand this cracks in buildings precursory phenomena theory.

Petra