by Seismological Society of America, APRIL 5, 2019
由美国地震学会，发布于2019年4月5日
Schematic depiction of hydraulic fracturing for shale gas, showing main possible environmental effects. Credit: Mikenorton/Wikipedia
页岩气水力压裂原理图, 显示主要可能的环境影响。图片来源: Mikenorton/维基百科
Two moderate-sized earthquakes that struck the southern Sichuan Province of China last December and January were probably caused by nearby fracking operations, according to a new study published in Seismological Research Letters.
《地震研究快报》(Seismological Research Letters, SRL)发表的一项最新研究表明，去年12月和今年1月在中国四川省南部发生的两次中等规模地震可能是由附近的水力压裂作业诱发的。
The December 2018 magnitude 5.7 and the January 2019 magnitude 5.3 earthquakes in the South Sichuan Basin caused extensive damage to farmhouses and other structures in the area. The December earthquake was especially destructive, injuring 17 people and resulting in a direct economic loss of about 50 million Chinese Yuan Renminbi (roughly $US 7.5 million).
在四川盆地南部发生的2018年12月的5.7级和2019年1月的5.3 级地震对该地区的农家和其他建筑造成了严重破坏。尤其是12月份的地震破坏很大，造成了17 人受伤、导致直接经济损失约5000万人民币（约750 万美元）。
图为正在进行钻井作业的涪陵页岩气平台。
The Changning shale gas block in the South Sichuan Basin has been the site of fracking operations since 2010, with extensive horizontal fracking injection wells becoming more common since 2014. The earthquake rate in the Changning block rose dramatically at the same time that systematic fracking began.
自2010年以来, 川南盆地长宁页岩气区一直是压裂作业场所。自2014年以来，广泛的工业化水平压裂喷射井越来越普遍。与此同时, 长宁地区的地震频度出现急剧上升趋势。
In the United States, wastewater disposal from oil and gas operations, where water produced during hydrocarbon extraction is injected back into rock layers, is thought to be the primary cause of induced earthquakes, especially in Oklahoma. However, there is growing evidence that hydraulic fracturing, or fracking, which uses injected water to break apart rock layersduring hydrocarbon extraction, may have caused moderate-size earthquakes at some sites in Ohio, Oklahoma and western Canada.
在美国，科学家们普遍认为石油和天然气产业的废水回注（油气提取过程
中伴生的水被注入深部岩层）是该区特别是俄克拉荷马州诱发地震的主要
原因。然而，越来越多的证据表明，在油气开采过程中通过高压注入水来
破碎岩层的水力压裂可能在俄亥俄州，俄克拉荷马州和加拿大西部的某些
地区诱发了中等规模的地震。
Both wastewater disposal and fracking have induced earthquakes in the south Sichuan basin, say Xinglin Lei of the Geological Survey of Japan and colleagues. In their new study in SRL, the researchers present "a full chain of evidence" to show that the December and January earthquakes were induced by fracking operations.
日本地质调查局的雷兴林和他的同事们认为，废水处理和水力压裂都引发了四川盆地南部的地震。在他们发表在SRL的新研究中，研究人员提出了“完整的证据链“，表明12月和1月的地震是由水力压裂作业诱发的。
They pinpointed the location of the earthquakes, finding that they were relatively shallow (between two and ten kilometers below the surface), as would be expected for induced earthquakes. The December and January quakes also coincided in time and space with injection at nearby fracking well pads. They did not have the exact injection volumes at these well pads to better understand the relationship between injection activities and the evolution of seismicity.
他们确定了地震的震源位置，发现地震相对较浅 (地表以下两到十公里)，符合诱发地震的预期深度。12月和1月的地震在时间和空间上也与在附近的水平井簇的压裂密切相关。当然，他们没有更精确的压裂数据来进一步理解注水与地震活动之间的关系。
Lei and colleagues' modeling of seismic activity show that most of the activity came from the initial mainshocks, with little aftershock activity, which is also consistent with the pattern seen for induced earthquakes. Finally, their calculations show that overpressure on the rock pores, produced by the fracking injections, was strong enough to activate preexisting faults in the region. These faults were mostly unmapped and not in a favorable orientation to slip under normal tectonic activity, the researchers note.
雷和同事对地震活动的统计建模分析显示，大部分地震活动来自最初的主震，余震活动很少，这也与典型的诱发地震的模式一致。最后，他们通过计算表明，水力压裂的高压注水对岩石孔隙产生的超压强到足以激活该地区先前存在的断层。研究人员指出，这些断层大多是未知的（没有地图绘制），在通常的构造应力下，断层的产状（延伸方向和倾斜角度）不利于滑动并会产生地震的。
"For most well pads, the associated seismicity fades out quickly after the hydraulic fracture ended or halted," said Lei, although he noted that their analysis did raise the possibility of seeing signs of fault reactivation from previous seismicity.
雷说，“对于大多数井场，相关的地震活动在水力压裂结束或停止后迅㏿
消失”。他进一步指出，相关的分析方法有助于从初期的地震活动中发现
断层被重新激活的迹象。
"In my opinion, repeated moderate earthquakes can be caused as long as the injection is continuing, since a moderate earthquake releases very limited strain," he added. "The national regulations in China should be updated with the requirement for operators to take action if some signs of fault reactivation were observed."
他补充说：“在我看来，对于被活化了断层，只要水力压裂持续，就可能
持续诱发中等强度的地震，因为中等地震释放的应变非常有限。有关部门
应该更新相应的国家法规，在观察到一定的断层活动迹象时，要求操作人
员采取必要行动。”
The researchers say more information is needed about faults and their stress patterns in areas of the Sichuan basin surrounding fracking well pads, to guide drilling in a way that would avoid moderate seismic activity. "Moderate earthquakes were observed in a limited number of sites," said Lei. "If these sites could be screened out, the risk of moderate earthquakes would be greatly reduced."
这几位研究人员表示，他们需要更多更详细的围绕压裂井场的断层分布及
其应力场信息，以研究如何避免破坏性地震的发生。雷说, “在四川盆地，
中等规模诱发地震发生在有限的几个井场附近。 如果可以事先筛选出这
些地点，破坏性地震的风险将会大大降低。”
Lei and colleagues would like to see researchers, regulators and oil and gas operators work together to better understand what causes injection-induced seismicity in the South Sichuan Basin, to allow effective and safe fracking operations.
雷和他的同事们希望研究人员、监管机构和油气运营商共同努力, 更好地了解是什么原因导致了四川盆地南部的注水诱发地震活动，从而为提高相应产业的有效性和安全性提供知见。。
