Earthquake Scale Range , The 1989 newcastle earthquake was an intraplate earthquake that occurred in newcastle, new south wales on thursday, 28 december.. All values ≤ magnitude ≤. The moment magnitude (mw) scale, based on the concept of seismic moment, is uniformly applicable to all sizes of earthquakes but is more difficult to compute than the other types. The effect of an earthquake on the earth's surface is called the intensity. The earthquake's magnitude is determined using the logarithm of the amplitude (height) of the largest seismic wave calibrated to a scale by a seismograph. Moment is a product of the distance a fault moved and the force required to move it. All values ≤ magnitude ≤. The moment magnitude scale is based on the total moment release of the earthquake. The 1989 newcastle earthquake was an intraplate earthquake that occurred in newcastle, new south wales on thursday, 28 december. Moment is a product of the distance a fault moved and the for