Two strong earthquakes shook the Island of Hawaii, Hawaii on the morning of October 15, 2006. Peak Ground Accelerations reached 1.2g, and earthquake felt intensity of MMI VIII. Earthquake damage of public and private property totaled about $200 million, with no fatalities. Geological engineering reconnaissance of earthquake damage resulting from the earthquakes focused on the apparent relationships between the observed geology and the damage. Some roadway embankments failed causing temporary closure of Island highways. Landslides were common at steep coastal cliffs. Liquefaction and lateral spreading occurred in coralline fill at Kawaihae Harbor. There were extensive road cut failures, in which the performance of road cuts in soil slopes was generally better than that of rock slopes. Where a’a clinker underlay massive a’a basalt blocks in road cut slopes, the loose clinker dislodged thereby undermining the blocks, and causing failures that blocked important roads. There was serious damage to stacked rock edifices such as the Hawaiian ritual temples of Pu’ukoholā and Mailekini. There are some parallels between the geomechanical behavior of clinker rock masses and the behavior of stacked rock structures: slope angle, slope height, particle size and nature and proportion of inter-particle contacts govern the seismic performance for both.