Answer: True
Step-by-step explanation:
A megathrust earthquake is a very strong and large earthquake that occurs in a subduction zone, a region where one of the earth's tectonic plates is thrust under another
The 1700 Cascadia earthquake is estimated moment magnitude of 8.7–9.2 The length of the fault rupture was about 1,000 kilometers (620 miles), with an average slip of 20 meters (66 ft).
While the California earthquake of April 18, 1906 ranks as one of the most significant earthquakes of all time. But the length of the fault rupture was about, 296 miles (477 kilometers) of the San Andreas fault from northwest of San Juan Bautista to the triple junction at Cape Mendocino.
Since the ruptured length of the coast of Oregon and Northern California (north of Mendocino California), is great than a San Andreas earthquake like 1906, so it magnitude likewise.