Earthquakes can be even smaller and even larger.
If an earthquake is felt or causes perceptible surface damage, then its intensity of shaking can be subjectively estimated. But many large earthquakes occur in oceanic areas or at great focal depths and are either simply not felt or their felt pattern does not really indicate their true size. Today, state of the art seismic systems transmit data from the seismograph via telephone line and satellite directly to a central digital computer. The only limiting factor is how long the seismic waves take to travel from the epicenter to the stations - usually less than 10 minutes. This amplification and recording as a function of time is the source of instrumental amplitude and arrival-time data on near and distant earthquakes.