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LARGEST QUAKES so far today -
5.0 VANCOUVER ISLAND, CANADA REGION
6.5 VANCOUVER ISLAND, CANADA REGION
5.1 SANTA CRUZ ISLANDS
Yesterday, 4/23/14 -
5.0 RYUKYU ISLANDS, JAPAN
5.1 NORTHERN MID-ATLANTIC RIDGE
5.0 BOUGAINVILLE REGION, P.N.G.
5.1 BOUGAINVILLE REGION, P.N.G.
5.0 BOUGAINVILLE REGION, P.N.G.
5.5 BOUGAINVILLE REGION, P.N.G.
5.5 LUZON, PHILIPPINES
5.1 ANDREANOF ISLANDS, ALEUTIAN IS.
5.2 OFF COAST OF TARAPACA, CHILE
5.1 OFF W COAST OF NORTHERN SUMATRA
5.3 BOUGAINVILLE REGION, P.N.G.
5.2 BOUGAINVILLE REGION, P.N.G.
5.1 BOUGAINVILLE REGION, P.N.G.
5.5 BOUGAINVILLE REGION, P.N.G.
8.2 Chile quake defied expectations - Smaller-than-expected tremor has scientists scrambling to redefine rules for areas of extreme seismic stress. Overnight on April 1, a series of quakes rocked the coast of northern Chile.
The 8.2 quake, which struck offshore near the village of Pisagua, was the largest in Chile since a magnitude 8.8 quake hit farther south in 2010. Although the Pisagua quake was not as big and not particularly damaging, it will still go down in the annals of seismology as an intensively studied earthquake that upends some assumptions about how and when big quakes happen.
In one sense, seismologists knew it was coming. Northern Chile, near the border with Peru, was the only stretch of the country’s coastline that had not broken in a large earthquake in the past century. In 2006, expecting it to go, a German–French–Chilean collaboration blanketed the region with seismometers, tiltmeters and other ground-measuring instruments, creating the Integrated Plate boundary Observatory Chile. It captured the Pisagua quake in action.
But the earthquake was not the ‘Big One’ that seismologists had expected. Only a monstrous earthquake, of around magnitude 9, would have relieved all the geological stress built up in the region. More quakes, on the order of magnitude 8, are still possible, but when they might strike is a mystery.
More broadly, the Pisagua event has seismologists rethinking some basic ideas about the risk of earthquakes in similar geological settings elsewhere - places with deep-diving crustal plates, such as Japan and Indonesia. Over time, earthquakes rupture particular portions of a long fault zone; the unbroken portions are ‘seismic gaps’ considered ripe for future quakes. Officials in these areas are often told to prepare for the worst-case scenario - the biggest possible earthquake in a given seismic gap.
But the Pisagua quake shows that this does not always happen. Instead, it underscores that seismic gaps can rupture in all sorts of ways, from lots of smaller quakes to just a few big ones. Chile is an ideal laboratory in which to study such questions because it lies on the margin of a subduction zone, where the Nazca tectonic plate dives - subducts - beneath the South American plate. Geological stress builds up and then is released in the occasional massive jolt.
Chile is home to the largest earthquake ever recorded — one of magnitude 9.5 in 1960 — and accounts for more than one-quarter of the planet’s total seismic-energy release. Pisagua had not seen a major earthquake since 1877, when a tremor of around magnitude 9 ripped through the area. Seismic activity began to pick up last August, when a swarm of small earthquakes struck the area. Another set followed over the new year, and a third cluster occurred in March. These three swarms seem to have prepared the subduction zone to rupture in the big 1 April quake.
Until recently, researchers had thought that the next large earthquake in northern Chile would break the entire interface between the Nazca and South American plate. The Pisagua quake and a magnitude 7.6 aftershock two days later, “are a clear counterexample of this simplistic classification." . Together they ruptured just a small portion of the entire region at risk.
Intriguingly, the part of the subduction zone that broke was not the part that had built up the most stress. For some reason, the Pisagua quake released stress in areas that were not the most wound up. “A lot of energy remains to be released in north Chile." When the next one comes, seismologists plan to be ready. IPOC has added instruments to capture aftershocks from the 1 April quake and whatever might happen next. Dozens of new seismometers and global-positioning stations have been deployed by teams from Chile, Germany and France.
Every little bit of data helps. Before the 1 April quake, one scientist thought that the northern Chile seismic gap would rupture either to the north or to the south of the Pisagua area, but not right through it. Now she has some fresh thinking to do. “Each of these efforts really does bring us a step forward." (map at link)
Papua New Guinea - Aftershocks in Bougainville after weekend quake raises landslip fears. In the Papua New Guinea island of Bougainville there are still tremors after Saturday night's large earthquake.
TROPICAL STORMS -
Current tropical storms - maps and details.
No current tropical storms.
SEVERE RAIN STORMS, FLOODING, LANDSLIDES -
U.S. Weekend tornado and severe weather outbreak coming for the Plains. A significant multi-day severe weather event is expected Saturday, Sunday, and Monday across the Central U.S. A strong low pressure system will trundle slowly across the region, spawning supercell thunderstorms capable of generating large hail, damaging winds, and a few strong tornadoes.
The action will begin Saturday afternoon along a swath from Central Texas northwards into Oklahoma and Kansas, then gradually shift eastwards on Sunday and Monday. Recent runs of the GFS and European model have been very consistent in showing moderate to extreme instability in the warm air ahead of the storm's cold front Saturday through Monday, and this weekend's severe weather outbreak has the potential to be the most dangerous one of this relatively quiet 2014.
This year has yet to spawn a killer tornado, setting a NEW RECORD FOR LATEST DATE OF THE YEAR'S FIRST KILLER TORNADO. The previous record belonged to 2002, when the year's first killer tornado struck April 21 (an F-3 that killed a man in a mobile home in a rural area of Wayne County, Illinois.)
The relatively cool and dry weather across Tornado Alley so far this year has led to no EF-3 or stronger tornadoes as of April 23, and that's also a RECORD-LONG WAIT SINCE MODERN TORNADO RECORDS BEGAN in 1950. "Serious efforts" to document all tornadoes began in 1953, which was the first full year of tornado watches issued by the U.S. Weather Bureau, now the National Weather Service.
An El Niño Watch continues - March featured neutral El Niño conditions in the equatorial Eastern Pacific, but NOAA has issued an El Niño Watch for the summer and fall of 2014, giving a greater than 50% chance that an El Niño event will occur by the summer.
"There remains considerable uncertainty as to when El Niño will develop and how strong it may become. This uncertainty is amplified by the inherently lower forecast skill of the models for forecasts made in the spring." None of the El Niño models (updated in mid-April 2014) predict La Niña conditions for peak hurricane season, August-September-October 2014, and 16 of 20 predict El Niño conditions.
Temperatures in the equatorial Eastern Pacific need to be 0.5°C above average or warmer for three consecutive months for an El Niño episode to be declared; sea surface temperatures were +0.2°C from average as of April 21. El Niño conditions tend to make quieter than average Atlantic hurricane seasons, due to an increase in upper-level winds that create strong wind shear over the Tropical Atlantic.
There is currently a Westerly Wind Burst over the equatorial Pacific Ocean that is helping push warm water eastwards towards South America. If this Westerly Wind Burst persists and expands eastwards through early May, the odds of an El Niño event will increase.
Arctic sea ice extent during March was 5th lowest in the 36-year satellite record. Temperatures in the Arctic were 2 - 6°C (4 -11°F) above average during the last half of the month, but a late-season surge in ice extent came as the Arctic Oscillation turned strongly positive the second week of March, with UNUSUALLY LOW SEA LEVEL PRESSURE in the eastern Arctic and the northern North Atlantic.
The associated pattern of surface winds helped to spread out the ice pack, keeping ice extent greater than it would have been. There was a modest increase in thick, multi-year ice over the winter, and the Arctic is in better shape to resist a record summer melt season this year than it was in 2013.
One billion-dollar weather-related disaster hit the Earth during March 2014: Southeastern Brazil's WORST DROUGHT IN 50 YEARS, which has cost at least $4.3 billion so far this year. This is the third most expensive natural disaster in Brazil's history, and the second consecutive year of disastrous drought in the country. Drought in Northeast Brazil during the first five months of 2013 caused an estimated $8 billion in damage - Brazil's second most expensive natural disaster in recorded history. Brazil's costliest natural disaster was the drought of 1978 ($2.3 billion in 1978 dollars, or $8.3 billion 2014 dollars.)
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