It’s Almost Over

The concern over the tsunami threat from Saturday’s magnitude 8.8 earthquake off the coast of South America has nearly run its course. Japan, like many other Pacific nations yesterday, is now examining the waves arriving on its shores and adjusting its priorities.

Monday 1st March 2010

After more than 24 hours of intense activity across the Pacific, the tsunami danger from the massive off-shore magnitude 8.8 earthquake near Concepcion in Chile is still running its course.

Most Pacific nations went on high alert as the tsunami disturbance passed through their territories on Sunday. Some, having experienced dramatic loss of life and damage during the Samoa – Tonga tsunami of September 2009, were particularly vigilant

Despite the massive nature of the Chilean earthquake, tsunami damage has been lighter than anticipated due to the waves being weaker than those experienced from the same source in the past.

Nevertheless, Japan and Russia went onto full alert as the waves traversed the western Pacific late Sunday. The warning for Russia was relaxed by the Pacific Tsunami Warning Centre at 8:57 p.m. last night, New Zealand time but Japan, which suffered loss of life during the 1960 Chilean tsunami, remained on alert.

Japan went on tsunami alert on Saturday morning New Zealand time when a shallow magnitude 7.0 earthquake struck 80 km east-south-east of Okinawa. Whilst a small tsunami was generated, the event was managed and damage was minimal.

Following the Chilean earthquake later the same day, tsunami waves of 1 to 3 metres, similar to those anticipated for arrival in New Zealand, were expected in Japan. Final arrivals remain to occur, but their experience seems to have been similar to ours in New Zealand.

Preliminary wave measurements are now being reported from Japan, with waves of 0.8 metres being recorded at Hokkaido at 7:36 p.m. Sunday night New Zealand time, and waves of 0.4 and 0.3 metres recorded at sites on Honshu around 7 p.m. NZDT. The island of Okinawa recorded a wave of 0.2 metres at 8:54 p.m. Sunday, New Zealand time.

Japan is nestled close to a major continent, and now awaits the effect as the trans-Pacific waves are reflected back from various landmarks after their trip across the Pacific. Unlike the rest of the Pacific where the waves simply passed though, Japan sits at the focus of the tremendous energy which has caused the sea waves to travel across the Pacific Ocean. After the waves pass their east-facing shores, Japan will need to monitor western shores in case the bulk of Asia causes wave activity to be to be focussed back eastward into the Pacific. However, initial serious concerns have eased.

Meanwhile, New Zealand’s Ministry of Civil Defence and Emergency Management has relaxed its alert status, downgrading its tsunami threat for New Zealand from a warning to a threat. This allows on-shore life to return to normal while those engaged in sea-based activities are warned that sea-level disturbances are still being experienced overnight.

Attention can now focus on the initial cause of the trans-Pacific disruption – the massive earthquake that occurred just off the coast of Chile.

[Compiled from data supplied by the U.S. Geological Survey and its contributing agencies, the U.S. National Oceanic & Atmospheric Administration’s Pacific Tsunami Warning Centre, and the Japan Meteorological Agency.]

One Response to “It’s Almost Over”

  1. Lizzie from Gizzie says:

    Was pleased to see that once again MOST Gisborne people did as they were told.

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