Science Japanese researchers detect gradual seafloor caving near Nankai Trough

[thomas]

A Japanese research team has reported, for the first time, observing the gradual annual subsidence of the seafloor near the Nankai Trough off Japan's Pacific coast. Using water pressure gauges from the Donet underwater earthquake and tsunami monitoring network, they detected subtle changes at two sites near the Kii Peninsula in central Japan.

Ongoing, long-term monitoring across multiple locations can improve understanding of the risks associated with large earthquakes and tsunamis. In this region, the oceanic plate is slowly sliding beneath the continental plate, causing the seafloor to be lowered over time. This gradual movement can eventually trigger a sudden slip at the plate boundary, potentially leading to a major earthquake and a subsequent tsunami.

For the issuance of tsunami warnings, the Meteorological Agency uses Donet water pressure gauges that translate increases in water pressure from a tsunami into height measurements. While subsidence can be detected through water pressure changes, the slight variations equivalent to a few centimeters per year had previously been indistinguishable from mechanical errors. The team led by Yuya Machida, a researcher at the Japan Agency for Marine-Earth Science and Technology, or JAMSTEC, has developed a mobile high-precision water pressure calibration device. They installed the device near a water pressure gauge at two locations off the Kii Peninsula, using laser measurements to assess minute height differences and comparing water pressure every six months to a year.

The researchers observed that the seafloor southeast and south of the Kii Peninsula was sinking at rates of roughly 1.5 and 2.5 centimetres per year, respectively. They noted that the boundary between the plates is not static; minor earthquakes can occur sporadically, and at times the plates shift gradually without causing any noticeable seismic activity.

Japanese team detect gradual seafloor caving near Nankai Trough

Long-term observations at multiple sites could aid in assessing the risk of major earthquakes and tsunamis.

www.japantimes.co.jp

 

[Ukigumo]

Oh dear! A prelude to an imminent earthquake?

 

[thomas]

Reported three days ago:

The probability of a megaquake occurring in the Nankai Trough within the next 30 years has been revised from 80 percent to a range of around 60 to 90 percent, or higher, Japan's earthquake investigation panel said Friday.

80% --> 60-90+%

What does this even mean, apart from the fact that they have no clue?

Gov't panel revises chance of megaquake in Nankai Trough to 60-90% - The Mainichi

TOKYO (Kyodo) -- The probability of a megaquake occurring in the Nankai Trough within the next 30 years has been revised from 80 percent to a range of

mainichi.jp

 

[mdchachi]

Basically it means they can say "told you so" if something happens. If nothing happens people will have forgotten the prediction by then.

 

[Ukigumo]

A

Basically it means they can say "told you so" if something happens. If nothing happens people will have forgotten the prediction by then.

A bit like Nostradamus/Astrology/palmistry, then?

 

[thomas]

"The government's latest probability figures for a long-expected Nankai Trough megaquake show that even Japan's best scientific minds still cannot accurately predict earthquakes."

The Earthquake Research Committee had previously said the probability of a magnitude 8-9 class quake occurring in the region within the next 30 years was around 80 percent. The panel now lists the likelihood as either "60 to 90 percent or higher" or "20 to 50 percent," depending on the calculation method used. The vagueness, acknowledged even by committee members, reflects both the limitations of current seismic forecasting and efforts to communicate scientific accuracy and integrity as transparently as possible.

Updated Nankai Trough quake estimates fuel uncertainty | The Asahi Shimbun: Breaking News, Japan News and Analysis

 

[Ukigumo]

Have they at least tried consulting the texts of Nostrodamus? Perhaps assessing the Emperor's palm might be fruitful?