Remember, it is not a question of whether or not there is an earthquake - there is one on its way. It is just a question of how intense it will be at your locality. This involves distance, as well as other factors, like soil type. But there will be a whole lot ofshakin' going on - somewhere.....

Timely and relevant.

Thomson Reuters Posted: Sep 22, 2017 1:08 PM PT

Magnitude 5.8 quake hits off northern California

Which is why there will be false alarms. Unless there is a location filter built into the EQ warning app, false alarms are guaranteed imo.

but there are some really important things. and they can be done in a very short time period.

1. Switch hospitals over to emergency generators immediately.

2. Turn off the power to the trains on the Metro.

3. alert the authorities at major airports.

if the alerts could be truly reliable, there are some positive things that would come out of it.

IMHO this is likely to travel a path similiar to the weather forecast.
I think that the alarms will get more reliable over time. Researchers will develop better models. On the consumer side there may be applications that evaluate data and forecasts to suggest appropriate actions (e. g. let me know about light shakes but wait with an alert until a treshold is reached). IoT may help to expand the sensor network and contribute to better data. I am conviced that there is a market for this.

I was proposing shutting the gas supply off to each home or other building by means of a spring loaded valve next to the gas meter.
It would be up to each homeowner to reinstate the supply. No question of cutting off and then restoring gas service to a large area.

Depends on where you live. Here, once the gas has been shutoff at the meter, only qualified gas fitter contractors or qualified gas company workers can turn the gas back on. If you turn the gas back on yourself and your house goes boom, don't count on any home insurance coverage.

Don't the meters already have a free flow preventer? IIRC the valves on tanks do.

ShakeAlert is a potentially very valuable system of early warning of earthquakes. How much warning you get depends on how far you are from the epicenter. For example, for a quake on the Seattle Fault (right under the city), there would be no warning at all. However, for a major quake offshore on the Cascadia Subduction Zone Seattle might get as much as 50 seconds of warning before damaging waves arrived. Since really powerful quakes in the M8 to M9 range effect large regions, a system like ShakeAlert could help many people over a wide area.

One big issue raised up-thread is false alarms. In a fully developed and fully operational ShakeAlert system this is addressed by using a dense array of many sensors. Software analyses the phase and amplitude of first arrivals at many stations. By analyzing the combined input from a large number of stations, the software can sort out small local quakes from large damaging ones. For a geek level discussion of this see the Virtual Seismologist Algorithm being developed at Cal Tech.

We don't yet have a sufficiently dense sensor network for a fully developed system. That will require additional funding. However the system is developed enough for beta testing. One thing that is being done in Seattle is to connect shake alert to a number of valves on the city's main water pipes. The fear is that in a large quake, if one or more of the main lines were severed, the water could rapidly drain out of the reservoirs. This is water that would be desparately needed in the days/weeks after the earthquake. There are currently shut off valves on the system, but they weren't designed to cope with an area wide disruption of the system. ShakeAlert could start closing all the key valves as soon as there is indication of a large quake. The beauty of this for beta testing is that if there were a false alarm, the valves could reopen quickly enough that there would be little or no significant effects for the city. At worst you might notice a brief drop in water pressure.

I wonder if the same could be done with natural gas. Shut the valves close to the source and let the downstream system pressure drop and if it was a false alarm, reopen the valves and bring the pressure back up before pilot lights went out. It's a thought.