International Collaboration and Training for the Assessment and Mitigation of Seismic Hazard in Iran

伊朗是世界上最容易发生地震的国家之一。在过去的50年里，发生了五次大地震，每一次都造成了1万多人死亡，最近的一次是2003年12月摧毁巴姆市的地震。几乎每年都会发生造成重大人员和财产损失的地震，例如2005年2月发生的扎兰德地震。试图减少地震造成的破坏的第一步是评估在特定地区发生地震的可能性。地震是在地壳内的断层上滑动发生的。它们是由断层两侧地壳块体的相对运动引起的。起初，摩擦使断层处于锁定状态；然而，随着时间的推移，断层两侧岩石的弯曲逐渐增大，直到它施加的力克服了断层上的摩擦。然后，断层两侧的岩石相互之间迅速滑动，辐射出地震波，导致附近地面剧烈震动。可以进行许多观测，以评估未来发生地震的可能性。确定所有活动断层的位置是一个重要的起点。这并不像在伊朗这样的国家看起来那么容易，在那里，许多断层没有露出地表，而是隐藏在地下。然而，在过去的地震中，地球表面的运动产生了陆地表面的特征，特别是断层周围的溪流和河流的格局，这些特征可以让我们找到以前没有认识到的断层的存在。由地球轨道卫星上的仪器进行的测量在这次搜索中发挥了重要作用。全球定位系统中的卫星可以用来测量微小的移动--每年几毫米到几厘米--因此我们可以探测到断层周围岩石的弯曲。使用雷达卫星的重复观测也测量了两次地震之间发生的缓慢地面运动。估计过去地震发生频率的最有效方法是将卫星测量与在高危地区进行的地面地质观测结合起来。为伊朗实施一项广泛的此类测量计划的任务是艰巨的。伊朗地质调查局(GSI)是负责评估伊朗地震风险的主要机构，但它缺乏开展此类计划的专业知识。然而，地震和构造观测与建模中心(COMET)的成员是这类观测方面的专家，彗星调查人员多年来一直与地球科学研究所合作，研究造山(构造)和地震科学的许多方面。因此，这项建议的目的是将年轻的伊朗科学家带到英国，在那里他们将在彗星内部接受适当技术的培训，并通过与彗星成员合作向他们学习。该提案的另一个部分是召开一次国际会议，聚集来自几个这样的国家的地质学家和地球物理学家进行危险评估所依据的观测，以及与规划大地震和减轻其影响有关的人员，以便分享经验并制定共同方法，将我们的结果传达给当地社区和地区当局。教育在减轻大地震影响方面的作用不容小觑。就最近在苏门答腊岛附近发生的大地震(2004年12月26日)而言，人们很好地认识到过去该地区存在这种地震，并了解这种地震将产生的影响。如果这一信息被成功地传达给当地社区和地区当局，那么，虽然地震是无法预测或预防的，但其破坏性的后遗症本可以大大减少。

Iran is one of the most earthquake-prone countries in the world. In the past 50 years, there have been five major earthquakes that have each killed more than 10,000 people, the most recent being the earthquake that devasted the city of Bam in December 2003. Almost every year there is an earthquake that does significant damage to people and property, e.g. the Zarand earthquake that occurred in February 2005. The first step in attempting to reduce the damage caused by earthquakes is to assess the likelihood of an earthquake occurring in a given area. Earthquakes occur by slip on faults within the earth's crust. They are caused by the relative motion of crustal blocks on each side of the fault. Initially friction holds the fault locked; however, with time, the bending of the rocks either side of the fault grows until it exerts a force that overcomes the friction on the fault. The rocks on either side of the fault then slip rapidly relative to each other radiating seismic waves and causing severe shaking of the ground nearby. A number of observations can be made to assess the likelihood of a future earthquake. Locating all the active faults is an essential starting point. This is not as easy as it might seem in a country like Iran where many of the faults do not reach the surface and remain hidden below ground. However, movement of the earth's surface in past earthquakes produces characteristic features in the land surface, particularly the pattern of streams and rivers around the fault, and these features can allow us to find faults whose existence had not previously been recognized. Measurements made by instruments on satellites orbiting the earth play an important role in this search. The satellites in the Global Position System can be used to measure small movements - a few millimetres to a couple of centimetres per year - and so allow us to detect the bending of rocks around the faults. Repeated observations using radar satellites also measure the slow ground motions occurring in between earthquakes. The most effective way to estimate how frequently earthquakes have occurred in the past is to combine satellite measurements with geological observations made on the ground in areas at risk. The task of carrying out an extensive programme of such measurements for Iran is a huge one. The Geological Survey of Iran (GSI) is the primary agency with responsibility for assessing earthquake hazard in Iran, but it lacks the expertise to undertake such a programme. However, the members of the Centre for the Observation and Modeling of Earthquakes and Tectonics (COMET) are expert in these types of observation, and COMET investigators have worked for many years with the GSI on many aspects of the science of mountain building (tectonics) and earthquakes. The purpose of this proposal is therefore to bring young Iranian scientists to the UK, where they will be trained within COMET in the appropriate techniques and learn from members of COMET by working with them. Another part of the proposal is for an international meeting that would bring together geologists and geophysicists making the observations on which the hazard assessment is based, and people concerned with planning for major earthquakes and mitigating their impact, from several such countries in order to share experiences and develop a common approach to communicating our results to local communities and regional authorities. The role of education in reducing the impact of major earthquakes is not to be underestimated. In the case of the recent large earthquake off Sumatra (26/12/2004), the existence of such earthquakes in that region in the past were well recognized and the effects that such an earthquake would produce were understood. If this information had been successfully communicated to local communities and to regional authorities, then, while the earthquake could not have been predicted or prevented, its damaging after effects could have been significantly reduced.