This is power vs. energy.

The Richter Scale is a logarithmic scale, based on shaking measurements (think of the old pencil-based seismograph!). Power. (10^1).

The Moment Magnitude Scale (the more modern/replacement of Richter Scale) is based on energy. Geological organisations reporting on an earthquake will usually show this as "M <number>" or "Mw <number>".

Richter works well for small-to-medium earthquakes, and it's not accurate for really large or distant earthquakes.

The energy released in an earthquake increases exponentially, not just linearly.

EDIT: The Moment Magnitude Scale is where the "10^1.5" figure is coming from. https://en.wikipedia.org/wiki/Moment_magnitude_scale