RAPID: Near-trench Deformation and Tsunami Runup from the Jan 3, 2010 Solomon Islands Earthquake

2010年1月3日，所罗门群岛部分地区发生里氏7.1级地震，造成强烈震动，引发当地山体滑坡和海啸，影响了几个岛屿，其中最著名的是泰特帕雷和伦多瓦。这场地震很可能是由2007年4月1日8.1级大地震引发的，而且发生在非常接近该地震东南部终点处的地方，这场地震本身就引发了一场严重的当地海啸，摧毁了许多沿海地区。最近这一次地震的独特之处在于，它引发了一场引人注目的海啸，在近1000公里外的两个海底压力传感器上都能识别出来，尽管它只是一个中等规模的7.1兆瓦的地震。这种不成比例的海啸激发是在中等规模(MW 7.5-7.8)的罕见海啸地震中观察到的，但这只表现出适度的慢速特征。人们提出了两种主要的可能性来解释2010年海啸事件的海啸激发：1)地震是一场“部分海啸地震”，因为它同时破裂了快分量和慢分量，使其能量矩比基本正常(现已建立的海啸地震判别式；或2)事件引发的强烈震动引发了海底山体滑坡，从而引发了海啸。这次地震的破裂很可能与2007年的地震相似，滑动主要发生在沿海沟最浅部分的离散斑块上，很像在海啸地震中观察到的滑动。我们将利用海岸环境非常接近破裂区域和海沟的特点，沿着地震最接近的两个岛屿，进行地震后海啸淹没和近震源大地形变调查，以确定这两个参数的大小和分布。大地测量将包括对隆起和裸露的珊瑚群落的短期静态和动态全球定位系统以及人类结构的下沉和淹没。还将评估SAR场景中覆盖受影响岛屿的可用干涉图。这些信息将对评估同震滑动是否单独导致了观测到的海啸的产生将是非常宝贵的，并将对发生在浅海沟内的即使是7级低震级事件引发海啸的可能性提供新的见解。海啸启动数据将(与美国国家海洋和大气局的研究人员合作)使用由综合大地测量技术约束的同震界面滑移模型进行建模。这一快速奖项得到了地球物理、海洋地质和地球物理以及岩土工程项目的支持。

On January 3, 2010 a moment magnitude, MW 7.1 earthquake occurred along a portion of the Solomon Islands, causing substantial strong shaking and triggering local landslides and a tsunami that impacted several of the islands, most notably Tetepare and Rendova. The event was likely triggered by, and occurred very near the southeastern terminus of the massive MW 8.1 earthquake of April 1, 2007, which itself caused a substantial local tsunami that devastated many coastal areas. This most recent event was unique in that it caused a notable tsunami that was identifiable on two ocean-bottom pressure sensors nearly 1000 km away, even though it was only a moderately large MW 7.1 event. Such disproportionate tsunami excitation is observed with moderately larger (MW 7.5-7.8) rare tsunami earthquakes, yet this exhibits only a modestly slow character.Two main possibilities are proposed to explain the tsunami excitation of the 2010 event: 1) The earthquake was a "partial tsunami earthquake" in that it ruptured both a fast and slow component, giving it a mostly normal energy-moment ratio (a now well established tsunami earthquake discriminant; or 2) Strong shaking from the event triggered a submarine landslide that generated the tsunami. It is likely that this event ruptured similarly to the 2007 event, with slip occurring primarily in discrete patches along the shallowest portion of the trench, much like slip observed in tsunami earthquakes. We will use the extreme proximity of coastal environments to the rupture area and trench to conduct a postseismic tsunami inundation and near-source geodetic deformation survey along the two most proximal islands to the event to identify the magnitude and distribution of both parameters. Geodetic measurements will include short-term static and kinematic GPS of uplifted and exposed coral communities and subsidence and submergence of anthropogenic structures. SAR scenes will also be evaluated for usable interferograms covering the affected islands. This information will be invaluable at assessing whether the coseismic slip alone was responsible for generating the observed tsunami, and will yield new insight into the potential for tsunami excitation from even low-magnitude 7 events occurring within the shallow trench. The tsunami run-up data will be modeled (in collaboration with researchers from NOAA) using the resultant coseismic interface slip model constrained from the combined geodetic techniques.This RAPID award was supported by the Geophysics, Marine Geology & Geophysics, and Geotechnical Engineering Programs.