Great quake rocks Japan, generating dangerous Pacific tsunami

We live on a dangerous planet. Earth's second great earthquake in thirteen months rocked the coast of Japan at 5:46 GMT this morning, generating a dangerous tsunami that is racing across the Pacific Ocean. The mighty magnitude 8.9 earthquake is the 7th most powerful tremor in world history (Figure 1), and the planet's second top-ten earthquake in the past two years. The world's 8th largest earthquake, a magnitude 8.8 event, hit Chile on February 27, 2010. Never before have two top-ten earthquakes hit so close together in time. Today's quake was the strongest in Japanese history, and may end up being the most expensive natural disaster in world history, surpassing the $133+ billion dollar price tag from Hurricane Katrina.


Figure 1. Wikipedia's list of strongest earthquakes of all-time.

Media reports put the height of the tsunami near the Japanese coast as high as 23 feet. The initial tsunami wave has already hit Hawaii, and so far wave heights have been less than six feet, with 2.1 feet measured at Honolulu and 5.7 feet on Maui. Hilo on the Big Island has had a wave of 4.6 feet thus far. The city is not going to suffer the kind of devastation wrought by the tsunami from the 9.5 Magnitude 1960 earthquake in Chile, killed 61 people in Hilo.

MEASUREMENTS OR REPORTS OF TSUNAMI ACTIVITY

BOSO JAPAN 02.5FT/00.75M
NAHA JAPAN 01.6FT/00.49M
OFUNATO JAPAN 10.7FT/03.25M
OMAEZAKI JAPAN 04.6FT/01.39M
TOKAI JAPAN 00.8FT/00.23M
TOSASHIMIZU JAPAN 03.0FT/00.91M
KWAJALEIN MARSHALL ISL 01.0FT/00.30M
MIDWAY IS. USA 05.1FT/01.55M
WAKE IS. USA 01.7FT/00.52M
LEGASPI PHILIPPINES 01.1FT/00.32M
DUTCH HARBOR AK 01.6FT/00.48M
NIKOLSKI AK 01.4FT/00.41M
FRENCH FRIGATE SHOALS 01.8FT/00.56M
ST PAUL IS. AK 02.0FT/00.61M
SAND POINT AK 00.7FT/00.22M
MANUS PAPUA NEW GUINEA 01.2FT/00.36M
NAWILIWILI KAUAI HI 01.6FT/00.48M
BARBERS POINT HI 02.3FT/00.70M
HONOLULU OAHU HI 02.1FT/00.64M
KAHULUI MAUI HI 05.7FT/01.74M
HILO HI 04.6FT/01.41M
KING COVE AK 02.1FT/00.64M
LANGARA POINT BC 00.8FT/00.23M

In the San Francisco Bay area, tsunami waves of 1.6 - 5.3 feet are expected near 8am local time. The highest waves are expected near Rio del Mar, in Monterey Bay near Santa Cruz. Fortunately, the expected time of arrival is near the time of low tide, and tidal range along the central California coast is about 5 feet. This means that in most locations, the initial tsunami wave will not reach above the high tide mark. However, a tsunami is usually a series of waves that occur over a period of hours, and the highest tsunami waves along the North American coast are expected to arrive 2 - 3 hours after the initial wave hits, according to the NOAA/NWS/West Coast and Alaska Tsunami Warning Center. These later waves could arrive as the tide is coming in, and cause flooding in low-lying areas. Northern California will see higher waves, with a tsunami of 7.9 feet expected at Crescent City. The waves will be hitting near the time of low tide at Crescent City, where tidal range is also about 5 feet between high and low tide.

Estimated time of arrival (PST) of possible tsunami at:
7:23 am for Crescent City
8:08 am for San Francisco
8:17 am for Santa Barbara

The latest forecast wave heights as of 5:20 am:
7.9 feet for Crescent City
6.5 feet for Port Orford
6.3 feet for Brookings
5.3 feet for Rio del Mar
4.5 feet for Reedsport
4.2 feet for Arena Cove
2.0 feet for Point Reyes
2.4 feet for Fort Point
2.8 feet for Pacifica
3.0 feet for Half Moon Bay
3.3 feet for Santa Cruz
2.9 feet for Point Sur


Figure 2. NOAA's preliminary forecast of tsunami wave energy for today's earthquake. Image credit: NOAA Tsunami Warning Center.

Portlight.org is mobilizing to provide financial assistance to people with disabilities affected by the disaster, and there will undoubtedly be a huge relief effort by numerous charities in the wake of the earthquake. Your financial contributions and prayers for those affected will be valuable.

Jeff Masters