Introduction to the earthquake
Magnitude：5.0 mb
Location uncertainty：18.341 S; 172.138 W
Depth uncertainty：10.0 km
Origin Time：2017-10-11 13:15:03.430 UTC
FE Region：TONGA REGION (174)
Depth
The depth where the earthquake begins to rupture. This depth may be relative to the WGS84 geoid, mean sea-level, or the average elevation of the seismic stations which provided arrival-time data for the earthquake location. The choice of reference depth is dependent on the method used to locate the earthquake, which varies by seismic network. The depth is the least-constrained parameter in the earthquake location, and the error bars are generally larger than the variation due to different depth determination methods.
Sometimes when depth is poorly constrained by available seismic data, the location program will set the depth at a fixed value.
longitude/latitude
An earthquake begins to rupture at a hypocenter which is defined by a position on the surface of the earth (epicenter) and a depth below this point (focal depth). We provide the coordinates of the epicenter in units of latitude and longitude. The latitude is the number of degrees north (N) or south (S) of the equator and varies from 0 at the equator to 90 at the poles. The longitude is the number of degrees east (E) or west (W) of the prime meridian which runs through Greenwich, England. The longitude varies from 0 at Greenwich to 180 and the E or W shows the direction from Greenwich.