Apupu platter is an assortment of appetizers commonly served at social gatherings in Hawaii. During one week in December 2023, island of Hawaii residents and visitors were treated to an assortment of earthquakes resulting from a variety of different geologic processes, like a pupu platter of earthquakes!
Thousands of earthquakes occur every year in Hawaii. These earthquakes are monitored by the USGS Hawaiian Volcano Observatory (HVO) and fall into three main classes: volcanic, tectonic and mantle.
Volcanic earthquakes are associated with magma moving within, and erupting from, active volcanoes. Tectonic earthquakes are associated with slippage along faults within the volcanoes, and along the décollement which separates the volcanoes from the underlying oceanic crust. Mantle earthquakes are associated with bending of the Earth’s crust and upper mantle due to the weight of the islands above.
The first earthquake in our pupu platter was a magnitude-5.1 event that occurred on Monday, Dec. 4 at 5:54 p.m. HST. It was located 9 miles (14 km) southeast of Volcano at a depth of 1 mile (2 km) below sea level. This was a tectonic earthquake related to shallow movement on the pali system of Kilauea volcano’s south flank. HVO received 1,180 felt reports from around the island of Hawaii and a handful from Maui, Oahu and even Kauai islands. Fortunately, no damage was reported. A magnitude-3.1 aftershock occurred four minutes later.
A magnitude-4.4 event then occurred on Wednesday, Dec. 6, at 5:17 p.m. HST. It was located 1 mile (2 km) west-northwest of Volcano at a depth of 14 miles (23 km) below sea level. It was likely a mantle earthquake related to flexing of the oceanic crust buried deep below the island. HVO received 383 felt reports for this event.
A magnitude-3.6 event then occurred on Thursday, Dec. 7, at 7:13 a.m. HST. It was located east of Pahala at a depth of 20 miles (33 km). The size, location and mechanism indicate that it likely was a mantle earthquake associated with the ongoing Pahala seismic swarm. This event got 69 felt reports.
Two days later, two different earthquakes occurred within one minute of each other. A magnitude-3.6 event occurred on Friday, Dec. 8 at 9:21 p.m. HST. It was located 2 miles (3 km) west-southwest of Holualoa at a depth of 8 miles (13 km) below sea level. This was likely a tectonic earthquake associated with slippage on a fault within Hualalai volcano. HVO received 464 felt reports, primarily from the Kona side of the island of Hawaii.
One minute later, a magnitude-3.4 event occurred 12 miles (19 km) north of Pahala at a depth of 4 miles (7 km) below sea level. This earthquake was likely a tectonic earthquake associated with slippage on the Ka‘oiki fault system between Kilauea and Mauna Loa volcanoes on the island of Hawaii. There were 44 felt reports for this event.
A magnitude-3.1 event occurred on Monday, Dec. 11 at 3:08 p.m. HST. It was located 13 miles (21 km) southwest of Laupahoehoe at a depth of 19 miles (31 km) below sea level. It was likely a mantle earthquake related to flexing of the oceanic crust deep below Maunakea. This event had 29 felt reports.
In addition to the widely felt tectonic and mantle earthquakes above, more than 400 volcanic earthquakes occurred beneath the summit of Kilauea from Dec. 4 through 11, with a peak of more than 200 events on Dec. 7. While numerous, these earthquakes were small and not felt. All were below magnitude-3.0 and most were below magnitude-2.0. These events were associated with the intrusion of magma beneath Kilauea summit.
This was a fascinating assortment of earthquakes from all around the island of Hawaii that, within the span of just one week, demonstrated different ways that earthquakes can be generated in Hawaii.
As always, HVO encourages you to submit a “Did You Feel It?” report if you feel an earthquake. Your felt reports contribute to earthquake intensity assessments generated by the USGS Earthquake Hazards Program and help us better understand the many processes that generate earthquakes in Hawaii.
Volcano
activity updates
Kilauea is not erupting. Its USGS Volcano Alert level is ADVISORY.
The unrest associated with the intrusion that began in early October southwest of Kilauea’s summit continues. Earthquake activity in Kilauea’s summit region over the past week remained relatively low. The Uekahuna tiltmeter — located northwest of the caldera — showed little net tilt over the past week, as did the Sand Hill tiltmeter — located southwest of the caldera. Unrest may continue to wax and wane with changes to the input of magma into the area and eruptive activity could occur in the near future with little or no warning. The most recent sulfur dioxide (SO2) emission rate for the summit — approximately 70 tonnes per day — was measured on December 5.
Mauna Loa is not erupting. Its USGS Volcano Alert Level is at NORMAL.
Webcams show no signs of activity on Mauna Loa. Summit seismicity has remained at low levels over the past month. Ground deformation indicates continuing slow inflation as magma replenishes the reservoir system following the 2022 eruption. SO2 emission rates are at background levels.
Two earthquakes were reported felt in the Hawaiian islands during the past week: a M2.7 earthquake 2 km (1 mi) SSW of Pahala at 31 km (19 mi) depth on Dec. 19 at 6:46 a.m. HST and a M3.0 earthquake 21 km (13 mi) SSE of Pahala at 33 km (20 mi) depth on Dec. 14 at 5:51 p.m. HST.
HVO continues to closely monitor Kilauea and Mauna Loa.
Email questions to askHVO@usgs.gov.
