Based on fault trenching work, geologists can use broken soils (that geologists date in a lab using charcoal) to identify past earthquakes. What is the average duration between Hayward fault earthquakes indicated by these data

140 years is average duration of an earthquake.

Explanation:

The Hayward fault is a geologic fault that is capable of massive destruction and is 119 km long fault western base of hills of San Francisco and is parallel to the San Andreas fault. The occurrence of an earthquake of 6.8 magnitudes in 1868 was biggest earthquake in California history.  Recently various geologists have taken time interval of the past five large earthquakes and based on the past earthquakes data the interval of 140 years it will take to the formation of a large earthquake.