Tuesday, March 8, 2011
7.2 earthquake hits off coast of Japan - A tsunami advisory has been issued in Japan after a 7.2 magnitude earthquake struck off the coast of Japan's main island of Honshu. The quake was centered 169 kilometers (105 miles) off the east coast of Honshu, directly east of the city of Sendai. The quake occurred about 8.8 miles below the earth's surface. The expected height of the tsunami was only expected to be 0.5 meters (19.6 inches). They could feel the earthquake in Tokyo, 267 miles southwest of the quake's epicenter, and the shaking lasted as long as three minutes, but there was no significant damage. TV Asahi showed video of boats rocking back and forth, as well as images taken from shaken city cams as the earthquake hit.
So far -
5.1 NEAR EAST COAST OF HONSHU, JAPAN
5.5 OFF EAST COAST OF HONSHU, JAPAN
5.7 NEAR EAST COAST OF HONSHU, JAPAN
7.2 NEAR EAST COAST OF HONSHU, JAPAN
There may be no such thing as a dormant volcano, according to scientists, who say that many could in fact be reawakened in a period of months. It has long been thought that once a volcano's magma chamber has cooled down, it stays dormant for centuries before it can be remobilized by fresh magma. But researchers have tested a theoretical model on two major eruptions and found that this process can take place in just a few months. The findings should lead to a reassessment of the dangerousness of some dormant volcanoes.
According to the team's mathematical model, reheating takes place in three stages. When fresh hot magma rises from below and arrives beneath the chamber, it melts the viscous magma at the base of the reservoir. This freshly molten magma therefore becomes less dense and starts to rise through the chamber, forcing the rest of the viscous mush to mix. This mixing process, they say, enables the heat to spread through the chamber a HUNDRED TIMES FASTER THAN PREDICTED by volcanologists.
The two researchers tested their model against the eruption of Mount Pinatubo in the Philippines in March 1991 and the ongoing eruption of the Soufriere Hills volcano in Montserrat, in the Caribbean. In both cases, seismic shocks preceding the eruption indicated the arrival of fresh magma beneath the cooling reservoir. By taking account of various known physical parameters of the two volcanoes - such as magma temperatures, size of the chamber and crystal concentration inferred from the study of magmas - the team was able to pretty much reproduce the time intervals between these warning signals and the eruptions. For Pinatubo, for instance, the mathematical model predicted that the underlying chamber could be reactivated within 20 to 80 days, whereas conventional theory gave a figure of 500 years. In reality, there was a gap of two months between the tremors and the eruption of the volcano.
HOW TO READ PROPAGATION NUMBERS
The A index [ LOW is GOOD ]
- 1 to 6 is BEST
- 7 to 9 is OK
- 11 or more is BAD
Represents the overall geomagnetic condition of the ionosphere ("Ap" if averaged from the Kp-Index) (an average of the eight 3-hour K-Indices) ('A' referring to amplitude) over a given 24 hour period, ranging (linearly) typically from 1-100 but theoretically up to 400.
A lower A-Index generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; a low & steady Ap-Index generally suggest good propagation on the 30, 40, 60, 80, & 160 Meter Bands.
SFI index [ HIGH is GOOD ]
- 70 NOT GOOD
- 80 GOOD
- 90 BETTER
- 100+ BEST
The measure of total radio emissions from the sun at 10.7cm (2800 MHz), on a scale of 60 (no sunspots) to 300, generally corresponding to the sunspot level, but being too low in energy to cause ionization, not related to the ionization level of the Ionosphere.
Higher Solar Flux generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; Solar Flux rarely affects the 30, 40, 60, 80, & 160 Meter Bands.
K index [ LOW is GOOD ]
- 0 or 1 is BEST
- 2 is OK
- 3 or more is BAD
- 5 is VERY VERY BAD
The overall geomagnetic condition of the ionosphere ("Kp" if averaged over the planet) over the past 3 hours, measured by 13 magnetometers between 46 & 63 degrees of latitude, and ranging quasi-logarithmically from 0-9. Designed to detect solar particle radiation by its magnetic effect. A higher K-index generally means worse HF conditions.
A lower K-Index generally suggests better propagation on the 10, 12, 15, 17, & 20 Meter Bands; a low & steady Kp-Index generally suggest good propagation on the 30, 40, 60, 80, & 160 Meter Bands.
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