Tonga
Photo by Nandeenee Naiken on Unsplash
TONGA: An M 8.2 +/- 0.3 is likely around May 16-19, 2026, within a 350-km radius of Pangai, Tonga, according to updates of the analytical research modules presented on this website as components of a new Ecological Model to anticipate the magnitude and timing of mainshock earthquakes
The largest recent earthquakes within 350 km of Pangai (2022-2026) were an M 7.3 in 2022 (236 km east of Pangai), an M 7.0 in 2025 (60 km south) and an M 7.5 on Mar 24, 2026 (186 km northwest of Pangai). These earthquakes are shown below on the Google Earth Pro map in relation to Tonga’s previous M 8.0 of 2006.
Information regarding the M 8.0 great earthquake of May 3, 2006, is available on the USGS network: M 8.0 - 47 km SSE of Pangai, Tonga: “At the location of the earthquake, the Pacific plate subducts westward beneath the Australia plate at a velocity of about 77 mm/yr”. This USGS site also says that a tsunami with wave height of 0.54 metres hit at Pago Pago, and that this peak was also reached at Crescent City, California. Fortunately, no loss of life was recorded, and only one person was injured.
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Figure 1.
Figure 1. Sequence of largest annual seismic events within 300 km of Tonga's M 8.0 in 2006, which provides the basic data for the Mainshock Analytical Module, and with the angles of the Triangular Analytical Module (red) superimposed on the graph for more clarity of that module which is being tested (angles are approximate). Together with the Foreshock Analytical Module this figure provides three separate estimates for the size of the forthcoming mainshock, as listed on the graph: their mean isM 8.21* and the 95% Confidence Limits (CL) are M 8.1-8.3.
*It is important to note that the final estimates of magnitude and timing are based on all the means (like the M8.21 above) acquired from a variety of different analyses, including different time periods and regions.
This and all subsequent graphs are done with GraphPad Prism and Spline analysis** used to fit smooth curves to the largest earthquakes in each period to stress the importance of 'flow' in understanding the population dynamics of earthquakes and the ability to forecast them.
**Data were analysed with a spline curve generated using GraphPad Prism version 5.01 for Windows,
GraphPad Software, San Diego, California USA, https://www.graphpad.com
This kind of graph is closely similar in format and concept to those of my previous career as an insect ecologist where, instead of the largest earthquake in a given time period, I was studying the maximum abundance of certain insect species each year as a result of different pasture grazing management practises. This simple approach led to a worldwide breakthrough which overturned conventional thought and expectations and made it possible to understand several previous conundrums in the dynamics of pasture pest problems throughout the world.
Well might you have asked: ‘What have insects to do with earthquakes?’ Nothing. and ‘What have earthquakes to do with insects?’ Nothing. Certainly not in this context here. But the ways an ecologist might go about modelling their population dynamics and features of their ecology are very similar.
Author's previous retrospective forecast for the M 8.0, 2006
This new ecological forecasting model gave the exact magnitude and date (May 3) for this mainshock which came, as expected, within 250 km of Pangai, Tonga. It occurred only 45 km SE of Pangai.
*If not stated otherwise, all earthquake data for the research and forecasts shown in this website were derived from the United States Geological Survey (USGS), and all times and dates are UTC.
This mainshock is imminent, but when?
—now likely as an M 8.2 ± 0.3 around May 16-19, 2026—
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Figure 2.
shows the sequence of largest yearly earthquakes within a radius of 500 km from Pangai, prior to Tonga’s M 8.0 of 2006. This analysis provides an opportunity to test the forecasts given by various modules (as shown) against a large mainshock which has already occurred, and the results are excellent with a mean forecast of M 8.03 based on estimates from the Mainshock Module, the Triangular Module, the Ratio Module, and the Foreshock Module.
The Triangular Module must have the 30-, 60- and 90-degree lines converging at the M 8.0 and large ‘foreshocks’ must occur on the 30- and/or 60-degree lines, as shown. The baseline joins the perpendicular side of the triangle at its intercept on the x-axis, and joins the hypotenuse at its intercept on the y-axis.
Please note the important comments in the caption to Figure 1 which apply to all estimates.
Author's previous retrospective forecast for the M 8.0, 2006. [See Figure 2, above.]
Key Findings from Figure 2:
Mainshock Analytical Module Performance
The author's Mainshock Analytical Module is robust, producing an estimate for the magnitude of the 2006 Tongan M 8.0 mainshock that closely matches the actual value. This reliability is notable given the unpredictable variation in event sizes throughout the sequence, where each data point contributes to the mathematical and statistical analyses. These analyses are grounded in a conceptual framework inspired by Newton's principle: for every action, there is an equal and opposite reaction.
Identification of the Critical Precursor
The lowest yearly magnitude recorded in the sequence of largest earthquakes for each year—the M 5.7 in 1974—is designated as the author's mathematical 'Critical Precursor' (CP) for modelling purposes. This designation is also conceptually based on the Newtonian principle outlined above.
Mathematical and Spatial Importance of the Critical Precursor
The Critical Precursor is both mathematically and spatially important. It typically occurs within several hundred kilometres of the subsequent mainshock. For example, with a search zone radius of 400 km, the CP was located only 125 km southwest of the M 8.0 mainshock. However, adjusting the size of the search zone can alter the CP's position accordingly.
Position of the Critical Precursor in Aftershock and Foreshock Sequences
The Critical Precursor usually lies at the divide between aftershock and foreshock magnitude sequences, as clearly seen in Figure 2.
Magnitude Drop Prior to Mainshock
A strong drop in magnitude in the penultimate year is the norm, and this pattern is clearly demonstrated in the sequence analysed.
Google Earth Pro map showing the location of the largest recent earthquakes in relation to the previous M 8.0 of 2006, within a radius of 350 km from Pangai, Tonga. https://earthquake.usgs.gov/earthquakes/map/
**Data were analysed with a spline curve generated using GraphPad Prism version 5.01 for Windows, GraphPad Software, San Diego, California USA, https://www.graphpad.com
This page is in process of being updated…
Latest update: 9 May, 2026.