By Arielle Emmett

With a little imagination, it’s not hard to see a natural hazard map of Indonesia as a dartboard with many bull’s-eyes. Throw a dart anywhere in the vicinity of the 18,000 islands that make up the Indonesian Archipelago, and it will almost certainly land close to more than one active volcano, and near areas severely impacted by past earthquakes and tsunamis, as well as dozens of fires, floods, tornadoes and landslides, which all routinely disrupt this country’s lush beauty.

Indonesia sits atop a tectonically complex region along the Pacific Ring of Fire — the volatile region of earthquake and volcanic activity that encircles the Pacific Ocean. And, by virtue of the archipelago’s equatorial location and its array of physiographically diverse islands, different parts of the country are subjected to a wide variety of weather, from drenching monsoon rains to prolonged dry spells.

I visited the islands of Java, Sumatra and Bali in December 2017 — my third visit to Indonesia in three years — eager to catch up on friendships and learn how carefully the country was monitoring its earthquake, tsunami and volcanic hazards. On my mind were the catastrophic 2004 Indian Ocean earthquake and tsunami that struck just west of Sumatra’s Aceh Province, claiming the lives of more than 170,000 Indonesians and roughly 270,000 people around the region.

In recent years, the Indonesian government, along with other groups like the Earth Observatory of Singapore and the U.S. Pacific Tsunami Warning Center, has been introducing technologies to improve hazard forecasting, warning and mitigation. Among these technologies are GPS systems enabling precision geodetic measurements of plate tectonic movements and stresses; tidal gauges; gas-sniffing drones and temperature sensors for volcanic monitoring; and a new set of integrated databases and communications systems providing hazard detection and visualization, decision support, and earthquake and tsunami warning protocols.

But how effective are these technologies in helping safeguard the country’s populace? Indonesia is a country with 55,000 kilometers of coastline and more than 266 million inhabitants living on 6,000 islands, many of which are among the most remote in the world, where cellphone and internet coverage is rare. I wanted to understand whether the government’s efforts to communicate about hazards were reaching its far-flung residents, and if disaster preparedness based on folklore and “local wisdom” might be equally important — or more so — than monitoring and warning technologies.

Weather and Geology Hazards

Few people outside the region understand just how regularly natural disasters occur throughout Indonesia’s 5,000-kilometer-wide archipelago. More than 2,000 serious disasters are reported each year, 90 percent of which are weather-related — mostly the result of flooding rains, tornadoes, fires and mudslides. In 2017, Indonesians reported 787 floods, 716 tornadoes, 614 landslides, and 96 forest and ground fires (burning peat lands and rainforests to make room for large palm oil plantations and smaller farms is a popular practice, especially in Sumatra). Indonesians also reported 19 regional droughts, two volcanic eruptions — at Mount Sinabung on Sumatra and Mount Agung on Bali — and 11 tsunamis. Overall, 3.4 million people were displaced that year by these natural disasters.

Indonesia experiences roughly 4,000 earthquakes a year, 70 to 100 of which are magnitude 5.5 or higher, along with one or two highly destructive quakes, some reaching or exceeding magnitude 8. Hazard maps created by the Indonesian Agency for Meteorology, Climatology and Geophysics, known as BMKG (Badan Meteorologi, Klimatologi, dan Geofisika), show that earthquakes and tsunamis are particularly frequent on those islands directly adjacent to the boundaries of the tectonic plates that meet in Indonesia’s midst — specifically the Indo-Australian, Pacific, Philippine Sea and Sunda plates — which are continuously moving and straining against one another.

Off the western and southern coasts of Sumatra, Java and Nusa Tenggara, for example, the Indo-Australian Plate subducts under the Sunda Plate at a speed of 5 to 7 centimeters per year, building up stress that’s occasionally released as large earthquakes. A chain of active volcanoes — including Sinabung and Krakatoa among others — traces this plate boundary. To Indonesia’s northeast, meanwhile, the Philippine Sea Plate collides with the Sunda Plate to its west and the Pacific Plate to its east. And between all of these major plate collisions, just east of Java, a so-called “suture zone” up to 2,000 kilometers wide comprises several smaller plates that move against each other at relatively high speeds. Earthquakes happen along multiple subduction zones and other faults in the suture zone, too, especially around the “spice islands” of Maluku, Sulawesi, Papua, and smaller islands in the Banda Sea.