Final answer:
Evidence for major fault movement includes large earthquakes and potential tsunami records, as these directly indicate fault activity. Sedimentary layers and volcanic eruptions are related to tectonic processes but are not direct evidence of fault movement.
Step-by-step explanation:
Evidence for major fault movement on the Seattle Fault zone around 1,100 years ago is best supported by the occurrence of a large earthquake that caused a significant change in topography, as well as possible tsunami activity. While sediments and radiocarbon dating of fossils are undoubtedly important in piecing together geologic events, they do not directly indicate the movement of fault zones. In contrast, the presence of tsunami records, which could have resulted from earthquake-induced displacement of the ocean floor, directly points to substantial fault movement. Similarly, volcanic eruptions can be associated with tectonic activity but are not direct evidence of fault movement unless the eruptions are triggered by the fault activity itself.
In the context of geological investigations, seismic surveys play a critical role by providing images of subsurface structures through the reflection of sound waves. Such surveys can indicate fault locations and movements. Moreover, geological formations such as accretionary prisms and sedimentary layers identified in seismic images also support the evidence of tectonic activity.