No pre-existing network. These things don't work unless you have a defined network where the people have already met to set up procedures.
Otherwise you're either lost in the immense bureacracy of countries like Sri Lanka or India trying to find someone with the authority to order an evacuation (mind you, the people you're calling have never met or heard of you....if you were them, would you believe them) or you're somehow trying to call the local police departments in the areas in question.
The below excerpt tells of a seismic station installed at the US military facility at Diego Garcia earlier this year. Stations are also in the Seychelles and Sri Lanka. It is not easy to learn what is done with the data.
http://www.igpp.ucsd.edu/ne/2004/02/09.html
Febuary 09, 2004
New IDA station installed in Diego Garcia
... installed the fortieth station in the IDA network on the island of Diego Garcia, British Indian Ocean Territory. The choice of Diego Garcia as a site for a seismic station was an obvious one to make: this atoll in the Chagos Archipelago is the only suitable land for over 1500 miles in any direction in the central Indian Ocean! IDA scientists strive to distribute their sensors in as globally uniform a fashion as possible given the distribution of continents and islands. Although great progress is being made at Scripps and elsewhere to install seismic instruments on the seafloor, the vast majority of seismometers are still installed on land. By placing instruments over a broad region of the globe, scientists can more accurately locate earthquakes and better develop detailed models of the Earth's interior by measuring the changes seismic waves undergo as they travel around the globe.
... The location for the sensors, in a seismic vault constructed on the US Air Force's GEODSS installation, provides a superb platform from which to view earthquake activity in this part of the world. Diego Garcia is located very close to very active seismic regions along the Southwest and Southeast Indian ridges. There are very few islands that can accommodate seismic instruments in the Indian Ocean. Project IDA has sites on four of them: in the Seychelles, Sri Lanka, Cocos (Keeling), and now Diego Garcia. ...