Complex sentence: The San Andreas Fault runs roughly parallel to the northeastern margin of Lake Cahuilla, where it moved at a rate of over the last 45,000-50,000 years, with earthquakes documented in sediments from Lake Cahuilla, but this southern segment has not ruptured in historical time.
Split into simpler sentences: The San Andreas Fault runs roughly parallel to the northeastern margin of Lake Cahuilla, where it moved at a rate of over the last 45,000-50,000 years. Earthquakes are documented in sediments from Lake Cahuilla, but this southern segment has not ruptured in historical time.