This animation shows every recorded earthquake in sequence as they occurred from January 1, 1901, through December 31, 2020, at a rate of 1 year per second. The earthquake hypocenters first appear as flashes then remain as colored circles before shrinking with time so as not to obscure subsequent earthquakes. The size of each circle represents the earthquake’s magnitude while the color represents its depth within the earth. This animation also highlights significant tsunamis generated by some of these earthquakes. When the following earthquakes appear they will also have their tsunami’s “energy map” that shows each tsunami's maximum modeled wave heights on the open ocean:
Note that while the great majority of all earthquakes occur at plate boundaries, these tsunami-causing earthquakes mostly occur at convergent plate boundaries. These boundaries, also called “subduction zones,” are where tectonic plates collide to produce megathrust earthquakes and are the regions where we expect future devastating tsunamis to come from. Other, much smaller earthquakes also occur away from plate boundaries such as those related to volcanic activity in Hawaii or those related to wastewater injection wells in Oklahoma.
The animation concludes with a series of summary maps. The first one shows all of the earthquakes in this 120-year period. The next map shows only those earthquakes known to have produced a tsunami, and the map after that shows only those earthquakes that produced damaging tsunamis. The final map shows the plate boundary faults responsible for the majority of these earthquakes.
he era of modern seismology—the scientific study of earthquakes—began with the invention of the seismograph in the late 19th Century and its deployment in instrument networks in the early 20th Century to record and measure earthquakes as they occur. Therefore, when the animation begins only the largest earthquakes will appear. They were the only ones that could be detected at great distances with the few instruments available at the time. But as time progressed, more and more seismographs were deployed and smaller and smaller earthquakes could be recorded. For example, the installation of these instruments in California in the 1930s creates the illusion of new earthquake activity there. Likewise, there appears to be a jump in the number of earthquakes globally in the 1970’s when seismology took another leap forward with advances in telecommunications and digital signal processing, a trend that continues today.