Geodetic observations at the early stage of subduction zone seismic cycle: towards complete seismic cycle coverage

俯冲带，如沿太平洋的那些？火环？产生地球？S最大、最具破坏性的地震，以及最多的海啸。2004年(苏门答腊岛)和2011年(日本)的大地震和海啸敲响了警钟，我们估计未来地震强度的能力仍然很弱。测量俯冲带附近的应变累积，现在可以用高精度的GPS装置，有可能预测未来地震的位置和大小。哥斯达黎加沿海的尼科亚半岛靠近海沟(70公里)，可以直接在地震孕育区进行观测。在这里，我建议升级和运行尼科亚半岛的一个连续的高精度GPS网络，并使用产生的数据来调查与俯冲带环境中的地震和海啸过程有关的一些问题。原则上，这类测量可以提供对未来地震和海啸的地点和规模的预测能力(时间可能仍然未知)。哥斯达黎加北部以快速俯冲(~8 cm/年)和短(50~60年)地震周期为特征，经常发生大地震(M7.5)，包括1853年、1900年、1950年(M7.7级)和最近的2012年9月5日(M7.6级)。该地区以前由美国国家科学基金会资助的研究已经确定了区域构造，并量化了地震旋回后期的一些关键孕震参数，包括震间应变积累和微震活动的模式，以及慢滑事件(SSE)的性质和时间。2012年的地震给了我们在地震周期开始时研究这些过程的机会，为科学界提供了一个描述完整地震周期的令人难以置信的机会。尼科亚C-GPS网络产生的所有数据都通过联合国志愿人员组织向公众开放，分析产品(例如同震和慢滑偏移距)可在我的网站(http://labs.cas.usf.edu/geodesy/))上获得，以帮助不熟悉全球定位系统处理细节的研究人员将这些数据用于地震研究。

Subduction zones such as those along the Pacific ?Ring of Fire? produce Earth?s largest and most destructive earthquakes, and most tsunamis. The giant earthquakes and tsunamis of 2004 (Sumatra) and 2011 (Japan) were wake up calls that our ability to estimate future earthquake magnitude remains weak. Measurement of strain accumulation in the vicinity of subduction zones, as is now possible with high precision GPS units, has the potential to forecast the location and size of future earthquakes. The coastal Nicoya Peninsula of Costa Rica lies close to the trench (70 km), allowing observations directly over the seismogenic zone. Here I propose to upgrade and operate a continuous high precision GPS network in the Nicoya Peninsula, and use the resulting data to investigate a number of questions related to seismic and tsunami processes in the subduction zone environment. In principle these kind of measurements could provide predictive capability in terms of location and size of future earthquakes and perhaps tsunamis (timing would still presumably be unknown). Northern Costa Rica is characterized by fast (~8 cm/yr) subduction and a short (50?60 year) earthquake cycle, producing frequent large (M7.5) earthquakes including events in 1853, 1900, 1950 (M 7.7) and most recently September 5, 2012 (M 7.6). Previous NSF-funded studies in this region have defined the regional tectonics and quantified a number of key seismogenic parameters at the late stage of the seismic cycle, including the pattern of interseismic strain accumulation and microseismicity, and the nature and timing of slow slip events (SSE). The 2012 earthquake gives us a chance to investigate these processes at the beginning of a seismic cycle, providing the scientific community an incredible opportunity to characterize a complete seismic cycle. All data generated by the Nicoya C-GPS network are made publicly available through UNAVCO, and analyzed products (e.g, coseismic and slow slip offsets) are available on my website (http://labs.cas.usf.edu/geodesy/) to assist researchers who are unfamiliar with the details of GPS processing use the data for earthquake research.