The cities facing the greatest danger of a mega-earthquake

    Increasingly crowded cities in poorer countries are more vulnerable than ever to massive earthquakes like the horrific, 7.8-magnitude tremor whose awful toll is still being counted in and around Kathmandu, Nepal. Some of the most seismically active regions in the world also happen to have infrastructure that has not improved with their rapidly rising populations, said David Wald, of the National Earthquake Information Center at the U.S. Geological Survey.

    In earthquake-prone cities, mushrooming populations are occupying buildings that are in many cases unable to withstand the effects of large quakes. Efforts to make buildings—or whole cities—safer are being outpaced by even faster growth in those places. (Tweet This)

    "You can pretty much pick a continent, and find a city or a country" at high-risk for damage, Wald said. The seismologist and research geophysicist named a handful of places relatively close to Nepal, but pointed to other regions as well. Wald mentioned, in no particular order:

Islamabad, Pakistan

Jakarta, Indonesia

Manila, Philippines

Tehran, Iran

Istanbul, Turkey

Quito, Ecuador

Lima, Peru

    "All things being equal, those vulnerable countries are 100 to 1,000 times, even 10,000 times, more vulnerable than a place like California."

All are located near active fault lines, and all have dense and, in many cases, growing populations. And all tend to lack the earthquake-safe construction needed to weather a large magnitude quake.

"All things being equal, those vulnerable countries are 100 to 1,000 times, even 10,000 times, more vulnerable than a place like California," Wald said.

    Wald's list of cities is only a provisional one—achieving an exact ranking or all-inclusive list would be difficult, Wald said, if not impossible. "One could list dozens of others, and actually ranking them is very difficult," he said.

Wald runs the Prompt Assessment of Global Earthquakes for Responseprogram for the USGS. The group provides estimates on fatalities and damage from earthquakes.

    A place such as California may suffer serious property damage during a large quake, but the number of lives lost would likely be a tiny fraction of what it would be in the least prepared regions, he said. Even Japan's buildings and structures were well protected from the massive 2011 quake that shook that country and caused a nuclear plant meltdown. (In that disaster, the subsequent tsunami took most of the lives.)

    Like others on the list, Kathmandu sits near an area of significant seismic activity—Nepal is near the fault where the Indian and Eurasian continental plates began colliding and forming the Himalayas 50 million years ago. 

Big quakes are less common in cities such as Tehran or Lima, but those cities have large numbers of people living in relatively unsafe structures—a critical factor that can make a quake much more catastrophic.

    The two deadliest earthquakes since 1980 were the 2010 quake in Haiti, which claimed more than 222,000 lives, and the 2004 Southeast Asian earthquake and tsunami that claimed 220,000 lives, according to data from reinsurance company Munich Re.

Many countries are trying to make improvements to protect busy cities. Turkey has been particularly aggressive, Wald said. And Nepal had undertaken many efforts to improve safety over the past decade, including retrofitting efforts at places such as schools, Wald said. Now researchers and aid organizations will take stock of which improvements worked and attempt to recreate them elsewhere, he said.