USGS HVO Press Release — Magnitude 4.1 Earthquake southeast of Maunaloa, Moloka‘i

According to Wes Thelen, HVO’s Seismic Network Manager, the earthquake was located 5 km (3 mi) southeast of Maunaloa, Moloka‘i. A map showing its location is posted on the HVO website at http://hvo.wr.usgs.gov/seismic/volcweb/earthquakes/. 

The depth of the earthquake was calculated to be shallow—less than 1 km (0.6 mi). However, determining accurate earthquake locations and depths in this region can be difficult because of the sparse coverage of seismometers on Moloka‘i and adjacent islands. Earthquake locations are most accurate when seismometers surround the earthquake source, which is nearly impossible given the geography of the islands in the area. Often, the depths are the most uncertain in these situations. Therefore, subsequent and more sophisticated analysis will likely result in locating this earthquake at a greater depth.

The earthquake was widely felt across the island of Moloka`i, as well as on east O‘ahu and west Maui. The USGS “Did you feel it?” Web site (http://earthquake.usgs.gov/eqcenter/dyfi/) received almost 90 felt reports within the first hour of the earthquake. Nearly all reports were of intensity 3 or less, indicating only weak shaking was felt. At these shaking intensities, damage to buildings or structures is not expected.

At the time of this release, no aftershocks had been reported felt. 

HVO’s seismic records show that in the past 25 years, there have been 5 earthquakes with magnitudes greater than 4 located north of Moloka‘i. Those 5 earthquakes, as well as today’s earthquake, are most likely a result of structural adjustments of the Earth’s crust and mantle due to the weight of the islands on top of it.

Earthquake activity generally decreases northwest up the Hawaiian Island chain. This earthquake is a good reminder that the potential for larger earthquakes still exists. Earthquakes of magnitude 6.4, 6.8, 6.4 and 6.5 occurred in the Moloka‘i region in 1870, 1871, 1895 and 1894, respectively. 

The 2nd annual Great Hawaii Shakeout, scheduled for 10:16 a.m. on October 16, 2014, is an opportunity for all Hawaii residents to practice “Drop, Cover and Hold On!”—actions that are proven to reduce injury in an earthquake. For details, please visit shakeout.org/hawaii/.

Daily updates about ongoing eruptions, recent images and videos of summit and East Rift Zone volcanic activity, maps, and data about recent earthquakes in Hawaii are posted on the HVO website at https://volcanoes.usgs.gov/observatories/hvo. 

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