MAGNITUDE-4.5 EARTHQUAKE STRIKES OFF KONA, HAWAIʻI
A magnitude-4.5 earthquake struck 33 miles west-southwest of Captain Cook, Kona, at 8:17 p.m. HST on July 9, 2026. The U.S. Geological Survey initially reported a 4.6 magnitude, later revised to 4.5. Hundreds of residents reported feeling the shake via the USGS “Did You Feel It?” platform. The Pacific Tsunami Warning Center confirmed no tsunami threat. No damage or injuries were reported.
Why No Tsunami? The Critical Role of Depth and Fault Type
Depth is the deciding factor. This quake occurred at approximately 40 km depth. Deep earthquakes, typically greater than 30 km, displace less seafloor vertically. This reduces tsunami generation significantly. Shallow quakes, like the 2011 Tohoku magnitude-9.0, displace the ocean floor massively. Deep quakes are “silent shakers” in tsunami terms.
The Kona quake’s depth placed it in the “deep” category for Hawaii. According to the “Volcano Watch: A deep dive into Hawaii’s deep earthquakes” column, these events are often linked to magma movement and lithospheric flexure, not slip on shallow faults. They rattle the surface but pose minimal tsunami risk.
The Science of ‘Silent Shakers’: Why Deep Quakes Are Less Dangerous
Seismic waves from deep quakes travel farther but lose force before reaching the surface. Energy dissipates through rock. Historical context shows Hawaii’s deep quakes, such as the 2006 magnitude-6.7 Kiholo Bay event, were felt widely but rarely triggered tsunamis. Deep quakes under Hawaii are volcanic in nature, related to magma chamber pressure, not plate boundary slip. This is why a magnitude-4.5 feels real yet remains harmless.
Earthquake felt off Hawaii Island: What Residents Should Know
Reports of shaking came from Kona, Waikoloa, and Hilo. The Hawaii Emergency Management Agency monitored the event but stood down. The Tsunami Center’s protocol only issues automated alerts for quakes greater than magnitude-6.5 near Hawaii’s coasts. Depth serves as a second filter. Deep quakes are reminders to check emergency kits and review tsunami evacuation zones—even when no threat exists.
Comparative Data: Deep vs. Shallow Quakes in Hawaii
| Parameter | Deep Quake (e.g., July 9, 2026) | Shallow Quake (e.g., 2018 Kilauea) |
|---|---|---|
| Depth | ~40 km | < 5 km |
| Tsunami Risk | Negligible | Moderate to High |
| Shaking Intensity | Widely felt, moderate | Localized, severe |
| Primary Cause | Magma movement, lithospheric flexure | Fault slip, volcanic activity |
How to Stay Safe During Future ‘Silent Shakers’
Drop, Cover, and Hold On is essential for any felt earthquake, regardless of depth. No tsunami warning does not mean no risk. Shallow quakes can follow deep ones. Always monitor official channels. Sign up for USGS “ShakeAlert” and HI-EMA alerts for real-time “earthquake now” updates. Prepare a go-bag and know your tsunami evacuation route. This applies even for deep quakes that might precede a larger event.
The July 9 deep 4.5 quake off Kona reminded Hawaii that not all rattles are tsunami threats. Understanding the science of “silent shakers” can reduce fear and improve preparedness. Stay informed: bookmark the USGS Hawaii earthquake map and subscribe to Hawaii News Now’s Tsunami Center updates for the next “earthquake now” event.
💡 Frequently Asked Questions (FAQ)
- Q: Why did the magnitude-4.5 earthquake off Kona not trigger a tsunami?
- A: The quake occurred at a depth of about 40 km, making it a deep earthquake. Deep earthquakes displace less seafloor vertically, significantly reducing tsunami generation. Shallow quakes, like the 2011 Tohoku magnitude-9.0, massively displace the ocean floor, while deep quakes are ‘silent shakers’ in tsunami terms.
- Q: What is a ‘silent shaker’ in the context of earthquakes?
- A: A ‘silent shaker’ refers to deep earthquakes that rattle the surface but pose minimal tsunami risk. In Hawaii, these events are often linked to magma movement and lithospheric flexure, not slip on shallow faults, so they dissipate energy through rock before reaching the surface.
- Q: What was the initial magnitude reported for the July 9, 2026 earthquake?
- A: The U.S. Geological Survey initially reported a magnitude of 4.6, but later revised it down to 4.5.
Extended Reading
For further details: “Magnitude-4.5 Earthquake Strikes Off Kona, Hawaiʻi” from Big Island Video News; “Volcano Watch: A deep dive into Hawaii’s deep earthquakes” from the Hawaii Tribune-Herald; and “Earthquake felt off Hawaii Island; no tsunami threat” from Hawaii News Now.