4.5 Molokaʻi Earthquake, No Tsunami

Maps provided by the USGS and Hawaiian Volcano Observatory showed different epicenter locations for the quake reported at 12:04 a.m. on Friday, June 21, 2013. Click image to view in greater detail.

By Wendy Osher

There is no tsunami threat to Hawaiʻi after a 4.5 preliminary magnitude earthquake reported at 12:04 a.m. on Friday, June 21, 2013, according to authorities.

The USGS initially reported that the epicenter was 2 miles WSW of Waikapū on the island of Maui; while data from the Hawaiian Volcano Observatory reported that the quake was centered off the north coast of Molokaʻi.

A subsequent update provided by the USGS said the epicenter of the quake was 30 miles north of Kualapuʻu, Molokaʻi.  Initial reports had placed the preliminary magnitude at 4.0, but that was later upgraded to a 4.5 by the USGS.

June 21, 2013 Maui County earthquake map posted by Pacific Tsunami Warning Center.

The exact updated coordinates of the epicenter provided by the USGS are as follows:

• 48km (30mi) N of Kualapuʻu, Molokaʻi, Hawaiʻi
• 78km (48mi) ENE of Kailua, Hawaiʻi
• 84km (52mi) ENE of Kāneʻohe, Hawaiʻi
• 86km (53mi) NNW of Lahaina, Hawaiʻi
• 93km (58mi) ENE of Honolulu, Hawaiʻi

21.596°N 157.007°W depth=34.7km (21.6mi)

The initial advisory dismissing any threat of a tsunami was released by the Pacific Tsunami Warning Center.

Additional information provided by the USGS:  (The text from the USGS Press Release issued at 9:37 a.m. 6/21/13 is posted below)

The US Geological Survey’s Hawaiian Volcano Observatory recorded a magnitude-4.5 earthquake located north of the Island of Moloka`i on Friday, June 21, 2013, at 12:04 a.m., HST.

The earthquake was located 34 miles north of Maunaloa, Moloka`i, at a depth of about 22 miles. A map showing the location of the earthquake is posted on the HVO website.

HVO’s seismic records show that 10 earthquakes of magnitude 3 or larger have occurred north of Moloka`i in the past 20 years, including a magnitude-4.1 earthquake on May 20, 2005.

Wes Thelen, HVO’s Seismic Network Manager, says that earthquakes in this area are not uncommon and are typically caused by a structural adjustment of the mantle in response to the weight of the Hawaiian Islands. “This is a good reminder that the Island of Hawai`i is not the only Hawaiian island prone to earthquakes,” he added.

No aftershocks have been recorded, and, according to Thelen, aftershocks typically do not follow earthquakes at these depths in the mantle.

Today’s earthquake was felt on several Hawaiian islands, from Maui to Kaua`i. The USGS “Did you feel it?” Web site received more than 60 felt reports within the first hour of the earthquake. Thus far, there have been no reports of damage.

The earthquake is not expected to have any effect on Kilauea’s ongoing eruptions. “HVO monitoring networks have not detected any significant changes in activity at the summits or rift zones of Kilauea or other Hawaiian volcanoes,” said Jim Kauahikaua, HVO’s Scientist-in-Charge.

The magnitude was initially estimated at 4.0, but more detailed seismic analyses resulted in a final magnitude of 4.5.

Due to a technical glitch, the USGS National Earthquake Information Center and Hawaiian Volcano Observatory webpages briefly posted two earthquakes north of Moloka`i, but only one earthquake occurred.