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鸿桦国际企业集团 - 人为诱发地震 美证实油气开采是主因

人为诱发地震 美证实油气开采是主因

  • 週四, 07 五 2015

人为诱发地震 美证实油气开采是主因

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<span class="st_blogger_hcount' st_url=" http:="" e-info.org.tw="" node="" 107206"="" st_title="人為誘發地震 美證實油氣開採是主因">
摘译自2015年4月26日ENS美国,维吉尼亚州,雷斯顿报导;姜唯编译;蔡丽伶审校

2009年起,美国中部和东部出现多起人为活动引起的地震。美国地质调查局(USGS)认为,这乃是油气业将废水或其他液体注入深井所致。

美国维吉尼亚州的一处钻油场。(来源:facesoffracking)

美证实:开采石油“诱发地震”

USGS科学家发现,美国8州共17处的“诱发地震”活动率增加。诱发地震指的是人类活动改变地壳压力和张力所导致的地震。

1973至2008年间,美国中部和东部平均每年仅出现21次规模大于3的地震。2009年至2013年暴增至美年99次规模3以上地震,活动率还持续升高。2014年总共发生659次规模3以上地震,大多介于3到4之间,虽有感但不致造成太大损失。部分州也曾出现规模5以上地震。

USGS首次针对这些诱发地震的危险性发表综合报告。频繁出现诱发地震的州有阿拉巴马州、阿肯色州、科罗拉多州、堪萨斯州、新墨西哥州、俄亥俄州、奥克拉荷马州和德州。目前发生次数最多的属堪萨斯州和奥克拉荷马州。

废水处置增加孔隙压力

石油和天然气生产过程会产生大量的废水。这些高盐份、化学物质污染的废水,将注入特别建造并经过核可的深井中,以防污染淡水水源,但这同时会增加地下孔隙压力。

USGS报告指出,孔隙压力增加可能导致附近断层滑动,增加地震发生机会。但报告也指出,虽然废水注入深井的作法可能引发地震,大多数深井不会引发有感地震。

有人怀疑水力压裂可能引发地震,但USGS认为,裂解过程并非有感地震的主因。

USGS分析诱发地震常见地区的地震活动率、地点、最大规模和地动方式,开发出可预测深井附近或其他诱发地震增加的工业作业地区地震的电脑模型,计算出接下来12个月的发生频率和震度。

报告中分析的17个地区,地震活动性增加的规律皆不尽相同。有些地区地震活动间歇性的发生,如德州科格德尔和科罗拉多州兰芝利。有些地区地震活动率呈现指数增加,持续至2015年。

Human-Caused Earthquake Hazards Jump in Eight States
RESTON, Virginia, April 26, 2015 (ENS)

The number of earthquakes triggered by human activities has soared since 2009 in the central and eastern United States. New research by the U.S. Geological Survey links the increase to industrial operations that dispose of wastewater or other fluids by injecting it into deep wells.

USGS scientists identified 17 areas in eight states with increased rates of “induced seismicity,” which means earthquakes and tremors caused by human activity that alters the stresses and strains on the Earth’s crust.

Between the years 1973–2008, there was an average of 21 earthquakes of magnitude three and larger in the central and eastern United States. This rate jumped to an average of 99 M3+ earthquakes per year in 2009–2013, and the rate continues to rise. In 2014, alone, there were 659 M3 and larger earthquakes . Most of these earthquakes are in the magnitude 3–4 range, large enough to have been felt by many people, yet small enough to rarely cause damage. There were reports of damage from some of the larger events, including the M5.6 Prague, Oklahoma earthquake and the M5.3 Trinidad, Colorado earthquake.

This report is the first comprehensive assessment of the hazard levels associated with induced earthquakes in the United States. These human-caused earthquakes are occurring in eight states: Alabama, Arkansas, Colorado, Kansas, New Mexico, Ohio, Oklahoma, and Texas.

The greatest number of induced earthquakes by far have been felt in Kansas and Oklahoma.

Large volumes of polluted wastewater can result from energy production, among other industrial processes. Wastewater that is salty or polluted by chemicals needs to be disposed of in a way that prevents contaminating freshwater sources. Deep well injection of wastewater increases the underground pore pressure.

The USGS report states that increased pore pressure may “lubricate nearby faults thereby making earthquakes more likely to occur.”

Although the wastewater disposal process has the potential to trigger earthquakes, most wastewater disposal wells “do not produce felt earthquakes,” the report states.

Questions have been raised about whether hydraulic fracturing, known as fracking, is responsible for the recent increase of earthquakes.

USGS studies suggest that “the actual hydraulic fracturing process is only occasionally the direct cause of felt earthquakes.”

The USGS report outlines a preliminary set of computer models to forecast how hazardous ground shaking could be in the areas where sharp increases in seismicity have been recorded located near deep fluid injection wells or other industrial activities capable of inducing earthquakes.”

The models aim to calculate how often earthquakes are expected to occur over the next 12 months and how hard the ground will likely shake as a result.

Scientists developed the models by analyzing earthquakes in these zones and considering their rates, locations, maximum magnitude, and ground motions.

Patterns of increased seismicity vary between the 17 different areas analyzed in the report. Some areas show pulses of increased activity interspersed between periods with little or no activity as in Cogdell, Texas, and Rangely, Colorado.

Other areas, such as central Oklahoma and southern Kansas, show exponential growth patterns of seismicity that are continuing in 2015.