2009年11月12日

India's lost water

Water resourses are at a premium in many parts of the world, and India is one of them.

Indirect evdence suggests that groundwater in being consumed faster than it is being naturally replenished in northwest Indea, but assessments of large-scale rates of depletion are difficult to construct from ground-based measurements.

Gravity observations from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites, combined with land surface models, have been used to produce a time series of groundwater strage variations in India.

The analysis reveals a progressively more severe reduction in groundwater in Northwestern India between 2002 and 2008.

Groundwater has been depleted at a mean rate of 4.0 cm of water per year averaged over the northern Ibdian states of Rajasthan, Punjab and Haryana.

The authors consider unsustainable consumption of groundwater for irrigation and other anthropogenic uses as the most likely cause.


### DataBace ###
nature Vol.460 925-1050 Issue no.7258 20 August 2009
Letter p999 / Satellite-based estimates of groundwater depletion in India / M Rodell et al.

posted by 0≠素子(由理政宗) at 15:35| earth | このブログの読者になる | 更新情報をチェックする

2009年10月26日

Calculating on the ice

Mass loss from marginal glaciers along the Greenland and Atrantic ice sheets is known to be contributing to sea-level rise but the precise magnitude and mechanisms are unclear, making it difficult to predict its potential future contribution to sealevel.

Surface mass loss is certainly a factor.

Ice loss from faster glacier flow ― called dynamical thinning ― has been more difficult to pin down.

High-resolution satellite altimetry measurements now show that dynamical thinning is for more important and extensive than previously thought, especially at ocean margins.


### DataBace ###
nature Vol.461 837-1018 Issue no.7266 15 October 2009
Letter p.971 / Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets / H D Pritchard et al.


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posted by 0≠素子(由理政宗) at 23:00| earth | このブログの読者になる | 更新情報をチェックする

2009年02月27日

Sesismic strees at Mentawai

In March 2005, just south of the rupture area of the 2004 great Sumatora-Andaman earthquake, the mangnitude 8.6 Sunde megathrust earthquake occurres. Concern then focused further south on the Mentawai area, wherelarge earthquakes had occurred in 1797 and 1833. A magnitude 8.4 and, twelve hours later, a magunitude 7.9 earthquake did indeed occur in September 2007. Konca et al. now show that the 2007 seismic crisis released only a fraction of the elastic strain that had accumulated since the events of 1797 and 1833, with the same protion of the megathrust rupturing in diffrent patterns depending on local factrors. The potential for a large megathrust event in the Mentawai area is therefore still high.

### DataBace ###
nature Vol.456 545-674 Issue no.7222 4 December 2008
Letter p.631 / Partrial rupture of a locked patch of the Sumatra megathrust durring the 2007 earthquake sequence / A O Konca et al. (California Institute of Technology)

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posted by 0≠素子(由理政宗) at 16:45| Comment(2) | earth | このブログの読者になる | 更新情報をチェックする
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