Magnitude Scale Magnitude US Geological Survey Richter Scale Magnitude and Depth Tsunami Generation Aftershocks Tectonic Plates U.S. Geological Survey Modified Mercalli Intensity Scale USGS Earthquake Reports San Andreas Fault Depth and Magnitude Seismic Waves Tsunami Formation Risk Analysis USGS Reports Intensity Scales Seismic Intensity Scale Japan Richterscale Magnitude 7.6 Earthquake Seismic Events Seismic Research Magnitude and Intensity of Earthquakes Tremor Analysis Tremors Impact Assessment Seismic Activity Intensity Scale USGS Earthquake Data Magnitude Scales Tsunami Warnings