How Did Chile Estimate the Earthquake Damage So Fast?

Within hours of Saturday’s devastating 8.8-magnitude earthquake, Chilean officials were already tallying up the damage. The Chilean minister of housing, Patricia Poblete, estimated Sunday that the earthquake had damaged 1.5 million homes. And in public statements on Sunday, officials said that the quake had damaged 500,000 homes and 1 million total buildings, displacing 1.5 million people. How do countries come up with these numbers so quickly?

They do it through the analysis of aerial photographs and estimates from sophisticated models — and in Chile’s case, likely both. In the past, before satellites and modeling programs, countries suffering from earthquakes would assess structural damage by extrapolating from on-the-ground estimates. For instance, a local government official would estimate the percentage of buildings destroyed in his neighborhood, and a regional or state office would collect the data to produce an estimate of aggregate destruction. Later, damage-assessment teams would refine the tally by hand. All that could take weeks.

But today, particularly in relatively wealthy and earthquake-prone countries — like Chile, Japan, and the United States — there is no need for such spit-balling. Governments use sophisticated modeling systems, such as the U.S. Federal Emergency Management Agency’s HAZUS, to produce accurate damage estimates within minutes of a terremoto.

Earthquake-system engineers start with electronic maps and satellite photographs, inputting geographical data on built structures, geographical features, and fault lines. Then they add in other variables, like what construction materials buildings use, how high they are, and population density. The system engineers can also include information about electricity sources, phone lines, dams, rivers, and other physical resources that might be damaged or disrupted by earthquakes. When even a tremor hits, the systems use its precise location and strength to extrapolate what kind of damage it might have caused.

Some earthquake-prone areas, like Kobe, Japan, now even incorporate 3-D versions of cities into models — both to help engineers find problem zones and enact prudential measures before earthquakes strike, and to more accurately determine an earthquake’s damage. Additionally, governments generally do not develop the systems themselves. Natural disaster damage forecasting has become an industry — with multinational companies, insurance giants, and governments all clients.

In Chile’s case, the 500,000 house, 1 million building, and 1.5 million person displaced numbers were likely flash estimates from computerized systems at Chile’s National Office of Emergencies, or ONEMI — the Chilean equivalent of FEMA.

For a more in-depth analysis of the extent of the damage, Chile has called in the services of the Global Earth Observation and Catastrophe Assessment Network (GEOCAN) — an umbrella group of earthquake experts founded in the wake of the Haiti earthquake by the World Bank and the Global Facility of Disaster Reduction and Recovery. GEOCAN obtains highly detailed satellite images of the afflicted area. Then civil engineers, architects, and other earthquake experts volunteer their time to help analyze and mark the images — crowdsourcing to get an accurate assessment of downed buildings, damaged roads, and off-line utilities.

But the computer models and satellite research don’t provide the granular detail that on-the-ground earthquake assessment teams can — what surgical units might be salvaged quickest, for instance. For that, Chile is relying on government officials, under ONEMI’s leadership, performing disaster assessments. It has also called in the U.N. Office for the Coordination of Humanitarian Affairs, which is sending in back-up teams.

Thanks to Stephanie Bunker of the U.N. Office for the Coordination of Humanitarian Assistance, the Earthquake Engineering Research Institute, and GEOCAN.