and feel with their own hearts.**
- Albert Einstein
LARGEST QUAKES -
Live Seismograms - Worldwide (update every 30 minutes)
This morning -
None 5.0 or higher.
5.1 EASTERN HONSHU, JAPAN
5.9 HOKKAIDO, JAPAN REGION
5.7 SOUTH OF KERMADEC ISLANDS
5.5 BALLENY ISLANDS REGION
5.7 KERMADEC ISLANDS REGION
TSUNAMI / FREAK WAVES / ABNORMAL TIDES -
Tsunami made worse by 'pop-up' of sediments - Tsunami created by undersea earthquakes can be made much larger by the "pop-up" movement of large amounts of sediment, research suggests. These quakes release huge amounts of energy as tectonic plates which stick as they pass each other suddenly slip.
But a study in Earth and Planetary Science Letters suggests that wedges of sediment scraped from the plates can pop up, boosting the resulting tsunami. It suggests that spotting these wedges could improve large tsunami prediction. Megathrust earthquakes are the sudden release of "elastic" energy stored as tectonic plates grind against each other, deforming but not slipping. Typically, as in the Japan earthquake of March 2011 that caused a massive tsunami and the Fukushima nuclear disaster, this occurs at a subduction zone, where one plate is sliding beneath the next. The quake arises when the deformation becomes too great and the stored energy suddenly releases. The sudden plate movement is transmitted into the ocean, inducing a tsunami.
"A Japanese submersible went down after the Tohoku earthquake and found not at all what everybody expected - which is that actually the tsunami was generated by the Japanese plate overriding the Pacific plate and moving upwards. But what this submersible found was... there was a fault which had moved the other way: instead of Japan moving upwards over the Pacific (plate), actually Japan had moved downward." Two researchers propose that the resulting tsunami was made far worse by the wedge-shaped "accretionary prism" at the boundary between the two plates. The prism is a collection of loose rock and mud that builds up gradually as one plate slips below another and fragments are broken off each.
When the plates finally violently slip, the point of the wedge is squeezed. This fires the material upward and outward, turning the energy of the plate into the energy of the ejected rock. "Let's say you have something wedge-shaped on the floor and you jump on it, the wedge will shoot sideways, and that's we think happens. The weight of the stuff on top shoots a wedge of stuff out. Put some water on the floor and do the same thing, and that will produce a wave."
The team went on to study the sites of other unexpectedly large tsunami from the past, including one off Nicaragua in 1992, Sumatra in 2004, and Java in 2006 - finding similar characteristics of the faults. That is promising, because it potentially provides a means to anticipate where the greatest tsunami risks lie - it is as simple as using submersibles to find faults that also have accretionary prisms. And because the resulting tsunami is more a product of the size of the prism rather than the size of the earthquake, the mechanism could explain why sometimes comparatively small earthquakes result in huge tsunami.
"There's a huge enterprise around the Pacific of predicting them, and the false alarm rate is very high - people evacuate a few times and then nothing happens. That's one of the reasons they're so dangerous - every now and again you have some little earthquake like one that didn't even wake people up in Indonesia but they heard the roar of the wave coming in, but the shaking was so small that they hadn't done anything."
TROPICAL STORMS -
In the Atlantic -
- Tropical storm Isaac was located about 65 mi [105 km] NE of Camaguey, Cuba. A Hurricane Warning is in effect for the Florida Keys, the West Coast of Florida from Bonita Beach southward to Ocean Reef and Florida Bay. A Hurricane Watch may be required for a portion of the northern Gulf Coast this morning. Isaac is expected to be at or near hurricane strength when the center reaches the Florida Keys. Additional strengthening is likely while the cyclone moves over the eastern Gulf of Mexico. It is too early to determine exactly where and when Isaac will make landfall along the Gulf Coast.
In the Western Pacific -
- Typhoon 15w (Tembin) was located approximately 350 nm southwest of Taipei, Taiwan.
- Typhoon 16w (Bolaven) was located approximately 110 nm southeast of Kadena AB, Japan.
'Igme' weakens and exits, but could turn back - Tropical cyclone Igme (Tembin) weakened into a tropical storm and exited the Philippine area of responsibility Saturday, but state weather forecasters said it may still make a U-turn and reenter Philippine territory.
Powerful typhoon approaches Okinawa - The Japanese island of Okinawa is hunkering down in preparation for wind gusts of up to 250km/h as Typhoon Bolaven approaches its shores.
Tropical Storm Isaac has swept into eastern Cuba after bringing flood misery to the south coast of Haiti, where four people were killed. The Cuban government declared a state of alert in at least six provinces and evacuated thousands of people from high-risk areas ahead of landfall. There were no reports of major damage in Haiti but heavy rain continued after the storm had passed.
In the US, a storm warning has been issued for the coast of Florida. Officials organised shelters and urged holiday-makers to leave the Florida Keys as the Governor declared a state of emergency to make sure emergency services would be ready when the storm made landfall today. The US Republican Party has delayed discussions at its National Convention in Tampa for a day because of the approach of Isaac. The Florida storm warning has now been extended north of Tampa. The storm is now located 550km (340 miles) east-southeast of Key West in Florida, moving north-west at 30km/h (17mph).
In Cuba's easternmost city, Baracoa, water crashed over the seawall and ran ankle-deep through the nearby streets. "We fear the sea and the flooding a lot more than the rain and wind. It rains frequently here all year long, but when the sea comes in, everything floods." In Haiti, a girl of 10 died when a wall fell on her in the capital, Port-au-Prince. There were three other known deaths.
The poorest country in the Americas is still recovering from the devastating 2010 earthquake and many of the 400,000 people still living in tent cities had no option but to weather the storm under canvas. "From last night, we're in misery. All our children are sleeping in the mud, in the rain." At one site, more than 50 tents collapsed, forcing people to search the mud for their belongings. (photo & map)
SEVERE RAIN STORMS, FLOODING, LANDSLIDES -
Burma floods leave 85,000 homeless. The Irrawaddy Delta - where 130,000 people died in a cyclone in 2008 - has been worst affected. UNUSUALLY heavy monsoon rains have inundated around 250,000 hectares of rice fields. Damaged transport and communications networks mean the full picture is still emerging.
The government says it has set up more than 200 emergency relief centres to help those who have had to leave their homes. Next year's rice harvest is also expected to be significantly affected. Rice is a key export for Burma and the staple diet for most of the population. The floods will test how reformed the new government in Burma is. When Cyclone Nargis devastated communities across the Irrawaddy Delta four years ago, the then-military government arrested those who reported the scale of the disaster and refused foreign help. This time, a civilian government which took power in 2011 and now includes opposition politicians is in charge.
EXTREME HEAT & DROUGHT / CLIMATE CHANGE -
West Africa forest biomass 'on rise despite drought' - The carbon storage capacity of protected forests in West Africa has increased despite the region suffering a 40-year drought, a study suggests. The tree composition in these areas favoured species that were able to cope with drier conditions. Previous studies suggested that drought conditions resulted in less carbon being stored as vegetation died.
Biomass is a vital component in the global carbon cycle. When plants grow, they absorb carbon dioxide and water in the photosynthesis process. While oxygen is released into the atmosphere as a waste product of this process, the absorbed carbon primarily remains locked in the plant until it dies. The study showed an increase in biomass. "Because you have got this long-term environmental shift, it is possible for the species composition of the forests to reshuffle slightly, so the species that can survive under those conditions are favoured. This means you are getting less negative impacts of the drought."
The West Africa region has experienced drought conditions since 1970. Rainfall has fallen by up to 23% compared with pre-1970 levels. "It is generally thought that if you have droughts then you are going to see a decrease in biomass. Certainly, studies that have looked at short-term, quite extreme droughts do seem to show biomass loss. It could be that the increase in biomass (recorded in this study) could be the result of something else, but we think that the maintenance of the forest structure, despite the drought conditions, is a result of a change in species composition. This basically means that you cannot take those short-term studies of extreme droughts and extrapolate the findings to a long-term event with different kinds of precipitation changes."
Findings earlier this year found that tropical forests in Africa may be more resilient to future climate change than the Amazon and other major forest regions. It suggested that the region's surviving tree species had endured a number of climatic catastrophes over the past 4,000 years. As a result, they were better suited to cope with future shifts in the climate. The continent's tropical forests form the second-largest continuous forested area in the world. "It is very important for the global carbon cycle that these forests are maintained."