Rapid recovery of high resolution topographic and kinematic data from the Kaikoura earthquake, New Zealand

2017年11月14日凌晨，新西兰南岛发生7.8级地震。地震开始于卡尔弗登以北约9公里处，断层面上的破裂沿着一系列9个独立的断层以复杂的模式迅速向北传播，剧烈的地表破裂(水平滑动长达10米)和凯库拉和布伦海姆之间的大规模滑坡。据记录，只有两人死亡，一人死于心脏病发作，另一人死于凯库拉一处历史悠久的宅基地倒塌。这场地震之所以引人注目有几个原因--它可能是发生在以水平运动为主的最大地震事件的时间和地点，当时有许多科学仪器已经在运行，以记录地震波并确定地面运动。地震主要发生在陆地上，这意味着我们或许能够从地震中被破坏和移动的道路和栅栏等特征中重建出运动感。此外，该事件是复杂的，有多个不同类型的断层上的滑动，短距离滑动的变化很大。然而，可以用来确定运动感的地表记录的许多方面都是相对短暂的。它们的大小和锐度逐渐减小，最终被表面过程破坏或扭曲，例如暴雨期间的坡面冲刷，以及修复高速公路和重新定位破碎的栅栏等人为补救措施。在地震期间发生的运动之后，一种称为震后滑动的较慢运动可能会在几周或几个月的时间尺度上发生。下一个冬季将会抹去许多更细微的地表特征。这些对于详细解释地震破裂是如何和何时发展的非常重要，包括断层陡峭和景观表面上的软特征，例如由砾石组成的地方。我们计划承担两项主要任务：i)在这些临时景观特征被地表过程破坏之前，尽快记录这些临时景观特征的关键实例，以帮助区分地震期间初始断层滑动和震后运动之间的区别；ii)安装一些半永久性GPS记录器，将它们的地面位置记录到几厘米以内，以捕捉约3个月的震后运动速度和时间。由于保存(风化和侵蚀)和污染(例如，地表以上沉积物的新沉积)的原因，这两项任务都严重依赖于时间。很快开展这项研究将使我们能够记录有助于了解地震事件细节的最大数量的数据。这有助于解释其他地震，并有助于更好地了解古代地震事件期间发生的事情，以便我们能够改进地震危险性评估。这有助于地方和中央政府以及公路、铁路、电力、供水等服务的当局和供应商更准确地规划未来的地震事件，从而改善这些地区公众可能面临的后果。

Early in the morning of 14th November 2017, a Magnitude 7.8 earthquake occurred in the South Island of New Zealand. The earthquake started around 9 km north of Culverden, and rupture on the fault plane propagated rapidly northwards in a complex pattern along a series of nine separate faults, with dramatic surface ruptures (with up to ~10m of horizontal slip) and large-scale landsliding between Kaikoura and Blenheim. Only two fatalities were recorded, one as a result of a heart attack, and one in Kaikoura when a historic homestead collapsed. The earthquake is remarkable for several reasons - it is probably the largest earthquake event dominated by horizontal movement to occur at a time and location where there were many scientific instruments already operating to record the seismic waves and determine the ground motion. The earthquake occurred mostly on land, meaning that we are may be able to reconstruct what the sense of movement was from features such as roads and fences that were broken and moved during the event. Furthermore, the event was complex, with slip on multiple faults of different type, and with large variations in slip over short distances.However, many aspects of the surface record which may be used to determine the sense of movement are relatively short-lived. They are gradually reduced in size and sharpness, and eventually destroyed or distorted by surface processes such as slope wash during heavy rain and by anthropogenic remediation such as repairing highways and repositioning broken fences. Following the movement that occurs during the earthquake, a slower motion known as post-seismic slip can occur on timescales of weeks and months. The next winter season will obliterate many of the finer surface features. These are very important for the detailed interpretation of how and when the earthquake rupture developed, and include soft features on fault scarps and landscape surfaces, for example where these are composed of gravel.We plan to undertake two main tasks: i) to record key selected examples of these temporary landscape features before they are destroyed by surface processes, as soon after the event as is possible, to help tell the difference between initial fault slip during the earthquake from post-seismic movement, and ii) to emplace a number of semi-permanent GPS recorders which record their ground position to within a few cm, to capture the rate and timing of post-seismic movement over a period of around 3 months. Both of these tasks are critically time-dependent for reasons of preservation (weathering and erosion) and contamination (e.g. new deposition of sediment above the surface features). Undertaking this research soon will allow us to record the maximum amount of data useful for understanding the detail of the earthquake event. This can help in interpreting other earthquakes, and in gaining an improved understanding of what happened during ancient seismic events, so that we are able to improve seismic hazard assessment. This assists local and central governments, along with authorities and suppliers of services such as roads, railways, power, water etc. to plan more accurately for future earthquake events, and consequently improve the likely outcomes for members of the public in those regions.