Magnitude 7.2 Earthquake Strikes Offshore Alaska Peninsula Region: At 10:48 p.m. Alaska time, on July 15, 2023, a magnitude 7.2 earthquake struck the offshore Alaska Peninsula region. This event reverberates the memory of the magnitude 7.8 Simeon of Earthquake that took place nearly three years prior, in the same vicinity. The recent quake was located 50 miles south of Sand Point, roughly 100 miles southeast of the previous magnitude 7.8 event, occurring at approximately 20 miles depth.
Immediate Response: Tsunami Warning
In response to the magnitude 7.2 earthquake that struck the offshore Alaska Peninsula region, authorities issued a tsunami warning. However, this was downgraded to an advisory level about an hour post-event, before finally being cancelled just before 1:00 a.m. The seismic activity resulted in tsunami waves reaching a maximum of 5 feet, recorded in King Cove and Sand Point. The ground shaking, reported to be of moderate intensity at the highest, was felt in multiple communities situated on the Alaska Peninsula and the eastern Aleutian Islands.
Contextualizing the Event: Connection to Previous Seismic Activity
The recent magnitude 7.2 earthquake that struck the offshore Alaska Peninsula region occurred within the zone of aftershocks from the previous magnitude 7.8 event. The aftershock activity from the earlier earthquake had greatly diminished since its peak in summer 2022. However, in 2023, the Earthquake Center noted an elevated level of seismic activity within this aftershock zone. Thus, it is possible to categorize the recent magnitude 7.2 earthquake as a late aftershock of the magnitude 7.8 earthquake.
Seismic Patterns: The Mechanism and Aftershocks
Like the Simeon of event, the mechanism of the recent magnitude 7.2 earthquake suggests fault rupture along the Aleutian megathrust fault. This significant seismic event is anticipated to generate its own aftershock sequence, similar to other moderate-sized earthquakes in the region. As of now, the largest aftershock, with a magnitude of 5.0, occurred a mere three minutes following the main shock.
Conclusion of Magnitude 7.2 Earthquake Strikes Offshore Alaska Peninsula Region
The magnitude 7.2 earthquake is not the only significant seismic event in recent history in this region. A major earthquake of magnitude 8.2 occurred on July 29, 2022, northeast of the Simeon of Earthquake epicenter. The rupture from this earthquake propagated northeast, moving away from the zone of the magnitude 7.8 event.
This recent flurry of seismic activity, including the magnitude 7.2 earthquake, within a span of three years has affected the subduction zone interface stretching from the Shumagin Islands in the southwest to Kodiak Island in the northeast. The Shumagin Island region had previously been recognized as a seismic gap — a region where no major earthquakes had occurred recently. However, these three large seismic events have partially filled this gap.
Q: What was the magnitude of the recent earthquake that struck the offshore Alaska Peninsula region?
A: The recent earthquake that struck the offshore Alaska Peninsula region had a magnitude of 7.2.
Q: When did the magnitude 7.2 earthquake occur?
A: The magnitude 7.2 earthquake occurred at 10:48 p.m. Alaska time, on July 15, 2023.
Q: What was the maximum recorded height of the tsunami waves triggered by the earthquake?
A: The maximum height of the tsunami waves recorded was .5 ft in King Cove and Sand Point.
Q: Is the recent magnitude 7.2 earthquake connected to any previous seismic activity in the region?
A: Yes, it occurred within the aftershock zone of the previous magnitude 7.8 Simeonof Earthquake.