Time-Dependent Earthquake Forecasts with a Tectonic Basis

研究人员正在准备、发布和测试地震预报，以解决有关浅层地震活动的一些基本问题，并提高对全球地震危险性的认识。 每一个预测都描述了一个大的区域（全球范围），甚至整个地球，并包括一个数字地图（或一组地图）的地震概率为特定的最小/阈值震级（S）和特定的时间段（S）。 强调大面积和适度的阈值震级意味着大量的实际地震可以与每个预测进行比较，并且可以定量评估相对成功（与零假设或更简单的模型相比）。 这项工作建立在两种不同的预测方法，每一种都基于对地震活动性的基本认识：地震在空间和时间上聚集（ETES模型）;地震发生在断层滑动和其他滞弹性应变的位置（ETES模型）。 在这个项目中，每个模型首先根据另一个模型的指导进行改进。 根据详细的运动学模型，正在研究五个构造带的短期地震聚集和触发。 此外，假定的长期地震活动与构造速率的比例关系（除了大洋中部的扩张上升）正在使用考虑到聚类的统计数据进行检验。 下一步是将两个预测模型合并，测试几种不同的可能组合，以创建具有构造基础的时间依赖性地震预测。 最后，研究人员将确定时间尺度，预测方法应该从主要基于聚类转向主要基于构造。 (This时间可能受局部构造应力积累速率的控制。） 每一个关于地震活动性（和/或特定参数值）的一般控制的假设最初都是通过对现有目录的回顾性测试来评估的。 通过这些测试的假设在地震可预测性研究合作实验室管理的正式前瞻性测试中进一步研究。 该项目正在创建一个新的组合预测算法，供加州地震概率工作组和其他类似小组审议，该算法提供从1年和5年预测到50年和500年预测的“无缝”过渡，满足各种社会需求。如果能够在全球范围内迅速实施更准确的地震预报，潜在的下游社会效益可能会很大。 该项目还试图解决关于地震活动性的一个最基本的问题：低地震活动性板块边界是永久性的，还是暂时的？ 这将指导下一代的假设，即是什么控制了凉爽的摩擦断层上的地震滑动和非地震滑动。

The investigators are preparing, publishing, and testing earthquake forecasts in order to resolve some basic questions about shallow seismicity, and improve knowledge of global seismic hazard. Each forecast describes a large region (of global scale), or even the entire Earth, and consists of a digital map (or set of maps) of earthquake probabilities for particular minimum/threshold magnitude(s) and for particular period(s) of time. The emphasis on large areas and moderate threshold magnitudes means that large numbers of actual earthquakes can be compared with each forecast, and relative success (compared to a null hypothesis or simpler model) can be evaluated quantitatively. This work builds on two different forecasting methods, each based on an elementary insight about seismicity: Earthquakes cluster in space and time (ETES model); and earthquakes occur at locations of fault slip and other anelastic strain (SHIFT model). In this project, each model is first undergoing refinement based on guidance from the other. Short-term earthquake clustering and triggering are being studied in five tectonic zones based on a detailed kinematic model. Also, the assumed proportionality of long-term seismicity to tectonic rate (except on mid-ocean spreading rises) is being tested using statistics that take account of clustering. The next step is to merge the two forecast models, testing several different kinds of possible combination, to create time-dependent earthquake forecasts with a tectonic basis. Finally, the investigators will determine the time-scales over which the forecast method should shift from primarily clustering-based to primarily tectonics-based. (This time is likely to be controlled by the local rate of tectonic stress accumulation.) Each hypothesis about general controls on seismicity (and/or specific parameter values) is initially evaluated by retrospective testing against existing catalogs. Hypotheses which pass these tests are further investigated in formal prospective tests administered by the Collaboratory for the Study of Earthquake Predictability. This project is creating a new combined forecasting algorithm for consideration by the Working Group on California Earthquake Probabilities and other similar groups, which provides a "seamless" transition from 1-year and 5-year forecasts to 50-year and 500-year forecasts, meeting a variety of social needs. The potential downstream social benefits may be large if more accurate earthquake forecasts can be quickly implemented on a global basis. The project is also attempting to resolve one of the most fundamental questions about seismicity: Whether low-seismicity plate boundaries are permanent, or temporary? This will guide the next generation of hypotheses about what controls seismic versus aseismic slip on cool, frictional faults.