Vanuatu: Magnitude-6.9 Earthquake Sparks Tsunami Fears

Vanuatu earthquake April 2016

A strong earthquake shook the Pacific island nation of Vanuatu early Sunday morning. Earliest reports put the magnitude of the Vanuatu earthquake at magnitude-7.2. It was subsequently lowered to 6.9 in a later notice.

The epicenter of the earthquake was located off the island of Espiritu Santo, about 253 miles (407 kilometers) northwest of Vanuatu’s capital, Port Vila, at 8:23 GMT, or about 7:23 p.m. local time on Sunday evening.

The town of Port Olry was the closest inhabited area, about 50 miles from the epicenter in the province of Sanma. Vanuatu’s population is about 270,000, including 44,000 in Port Vila. The USGS (United States Geological Survey) estimates that about 187,000 people felt the effects of the earthquake, with about 3,000 of them experiencing strong tremors. Warnings were issued by the Pacific Tsunami Warning Center and the Vanuatu Meteorology and Geo-Hazards Department for possible “hazardous tsunami waves” within 186 miles or 300 kilometers of the earthquake’s epicenter. In response to the earthquake, authorities in Vanuatu evacuated coastal areas in the provinces of Torba, Sanma, Penama, and Malampa. The warnings were lifted by 11 p.m. local time. “Based on all data available… the tsunami threat from this earthquake has now mostly passed,” the Pacific Tsunami Warning Center indicated in a prepared statement.

The USGS (United States Geological Survey) initially measured the earthquake at a depth of 6 miles or 10 kilometers. It was later adjusted to about 21 miles or 35 kilometers. The depth is significant because the shallower the earthquake, the more damage that it typically causes.

The Vanuatu Meteorological Services indicated there were no initial reports of injury or damage in Vanuatu or the surrounding area, despite the strength of the earthquake, as reported in the Hindustan Times. That in itself is not unusual. A magnitude-7.3 earthquake struck the Vanuatu region in October, and another magnitude-6.3 earthquake rocked the region in December. Neither caused significant damage or tsunami waves.

Vanuatu is certainly no stranger to earthquakes or other seismic activity. It lies in a volatile area of the South Pacific ocean known as the Ring of Fire. The so-called Ring of Fire is a string of volcanoes located along the tectonic plates in the Pacific Ocean in what are termed “subduction zones.” At these junctures, one tectonic plate is forced underneath the adjacent plate, creating the volatile conditions where volcanoes form and earthquakes are common. Vanuatu is located in the region where the eastern part of the Australia plate bumps up against the Pacific plate, with the Alpine Fault line running near New Zealand. There have been 15 earthquakes of magnitude-7.5 or greater recorded in the area since 1900. In August of 2011, Vanuatu was struck by two powerful earthquakes measuring 7.1 and 7.4 in magnitude, and tsunami waves of about 3.4 feet were observed on one of the islands.

The region is also prone to cyclone activity. Just over a year ago, Vanuatu was hit by devastating cyclone Pam that caused widespread damage. The frequency of seismic activity and other natural hazards along with a lack of resources and preparedness led the United Nations University to rank it as the world’s most at-risk country for natural disasters on the UN University World Risk Index.

Despite lifting the tsunami alert, earthquakes and aftershocks continue to rock the Vanuatu area into Monday morning. A second tremor measured at magnitude-4.8 occurred several hours later, at 12:19 GMT, 91 kilometers northwest of Port Olry, and another earthquake measured at magnitude-5.0 occurred southwest of Sola, Vanuatu, about four hours later.

[Image via USGS]