This is known from radiometric dating of rocks sampled from the seafloor during the Deep-Sea Drilling Project and through the use of magnetic stratigraphy and magnetic stripes as described above. The oldest seafloor is no more than 180 million years old. The surface area of the Earth is not growing. The above two imply that lithosphere must be destroyed somewhere. Plate tectonics says it is destroyed in subduction zones.
Most earthquakes occur in narrow belts.
These belts are found along the mid-ocean ridges, deep seafloor trenches, and transform faults. Also, there are deep earthquakes near the world's deep ocean trenches. You can use magnetite compasses to estimate the location of the geomagnetic poles at the time your rock sample formed. If you estimate the APWP from Europe and North America, they are different, but if you correct for plate tectonics, you find the paths are quite similar. There are additional lines of evidence described in your book and in This Dynamic Earth .