Geological Engineering Reconnaissance of Damage caused by the October 15, 2006 Hawaii Earthquakes, by E.W. Medley (2007)

Title:

Authors:

Edmund W. Medley, Senior Consultant, Geosyntec Consultants Inc., Oakland,
California, USA

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.