Categorized | Earthquake, Featured, News

Pair of quakes shake the Big Island early Saturday morning (May 9)

A 3.1 magnitude quake struck in the Hawaii Volcanoes National Park area at 2:17 a.m. Saturday, May 9, 2015.

A 3.1 magnitude quake struck in the Hawaii Volcanoes National Park area at 2:17 a.m. Saturday, May 9, 2015.

Magnitude
3.1

Time
2015-05-09 12:17:55 (UTC)
2015-05-09 02:17:55 HST

Nearby Cities
7km (4mi) SW of Volcano, Hawaii
40km (25mi) SW of Hawaiian Paradise Park, Hawaii
44km (27mi) SSW of Hilo, Hawaii
80km (50mi) ESE of Kailua-Kona, Hawaii
343km (213mi) SE of Honolulu, Hawaii

A 4.5 magnitude quake struck west of Pahla at 2:18 a.m. Saturday, May 9, 2015.

A 4.5 magnitude quake struck west of Pahla at 2:18 a.m. Saturday, May 9, 2015.

Magnitude
4.5

Time
2015-05-09 12:18:48 (UTC)
2015-05-09 02:18:48 HST

Nearby Cities
14km (9mi) WSW of Pahala, Hawaii
69km (43mi) SE of Kailua-Kona, Hawaii
82km (51mi) SW of Hawaiian Paradise Park, Hawaii
84km (52mi) SW of Hilo, Hawaii
336km (209mi) SE of Honolulu, Hawaii

A pair of temblors rocked the Big Island early Saturday morning (May 9). At 2:17 a.m. a 3.1 magnitude quake struck the Hawaii Volcanoes National Park area while a second quake of 4.5 magnitude shook a minute later at 2:18 a.m. west of Pahala.

The quakes were felt island-wide according to the USGS ‘Did you feel it?’ website reports. Numerous reports came in as far away from the epicenter as Honokaa.

Seismic recordings in Hilo of Saturday morning's quakes on May 9, 2015.

Seismic recordings in Hilo of Saturday morning’s quakes on May 9, 2015.

Magnitude 4.5 Earthquake North of Nāʻālehu

By USGS/HVO

The U.S. Geological Survey’s Hawaiian Volcano Observatory (HVO) recorded a magnitude-4.5 earthquake located in the Kaʻū District of the Island of HawaiÊ»i on Saturday, May 9, at 2:18 a.m., HST.

According to Wes Thelen, HVO’s Seismic Network Manager, this earthquake was centered about 8 km (5 mi) north of Nāʻālehu at a depth of 9.7 km (6.0 mi). A map showing its location is posted on the HVO website at http://hvo.wr.usgs.gov/seismic/volcweb/earthquakes/.

The earthquake was widely felt on the Island of HawaiÊ»i. The USGS “Did you feel it?” Web site (http://earthquake.usgs.gov/eqcenter/dyfi/) received over 70 felt reports within an hour of the earthquake. Light shaking (Intensity IV) has been reported across the island. At these shaking intensities, damage to buildings or structures is not expected.

Three aftershocks (magnitudes 1.6, 1.5, 1.4) of the earthquake were recorded as of 3:30 a.m., HST. Additional aftershocks are possible and could be felt.

Over the past 30 years, the area north of Nāʻālehu has experienced 6 earthquakes, including today’s event, with magnitudes greater than 4.0 and at depths of 5–13 km (3.1–8.1 mi). This area of Kaʻū is a seismically active region where a magnitude-6.2 earthquake occurred in 1919. Areas adjacent to this morning’s event experienced earthquakes of magnitudes 6.0, 7.1, and 7.9 in 1868.

The depth, location, and recorded seismic waves of today’s earthquake suggest a source on the large fault plane between the old ocean floor and overlying volcanic crust, a common source for earthquakes in this area.

The earthquake caused no detectable changes in KÄ«lauea Volcano’s ongoing eruptions, on Mauna Loa, or at other active volcanoes on the Island of HawaiÊ»i. A magnitude-3.1 earthquake that occurred in KÄ«lauea Caldera about one minute before the magnitude-4.5 earthquake was unrelated to the Nāʻālehu event.

For information on recent earthquakes in Hawaii and eruption updates, visit the USGS Hawaiian Volcano Observatory website at http://hvo.wr.usgs.gov

USGS: How large does an earthquake have to be to cause a tsunami?

Magnitudes below 6.5
Earthquakes of this magnitude are very unlikely to trigger a tsunami.

Magnitudes between 6.5 and 7.5
Earthquakes of this size do not usually produce destructive tsunamis. However, small sea level changes may be observed in the vicinity of the epicenter. Tsunamis capable of producing damage or casualties are rare in this magnitude range but have occurred due to secondary effects such as landslides or submarine slumps.

Magnitudes between 7.6 and 7.8
Earthquakes of this size may produce destructive tsunamis especially near the epicenter; at greater distances small sea level changes may be observed. Tsunamis capable of producing damage at great distances are rare in the magnitude range.

Magnitude 7.9 and greater
Destructive local tsunamis are possible near the epicenter, and significant sea level changes and damage may occur in a broader region.

Note that with a magnitude 9.0 earthquake, the probability of an aftershock with a magnitude exceeding 7.5 is not negligible. To date, the largest aftershock recorded has been magnitude 7.1 that did not produce a damaging tsunami.

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