The depth of the earthquake is 20 miles below the surface. I’m not sure if there would be huge levels of damage. If that earthquake was 10 miles below the surface, then the damage and casualty toll would be huge.
Here’s a link that shows the depth was only 10 kms (6.2 miles) : http://earthquake-report.com/2013/10/15/very-strong-earthquake-mindanao-philippines-on-october-15-2013/
That’s fairly shallow, and if that’s accurate, there could be some significant damage and regrettably, loss of life.
Ray, the depth is 56.8 KM or 35 miles deep and is considered a shallow quake.
Shallow earthquakes are between 0 and 70 km deep; intermediate earthquakes, 70 - 300 km deep; and deep earthquakes, 300 - 700 km deep. In general, the term "deep-focus earthquakes" is applied to earthquakes deeper than 70 km. All earthquakes deeper than 70 km are localized within great slabs of shallow lithosphere that are sinking into the Earth's mantle.
USGS: Measuring the Size of an Earthquake