Mid-ocean microseisms
Mid-ocean microseisms
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DOI：
10.1029/2004gc000768
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发表时间：
2005-04-20
影响因子：
3.5
通讯作者：
Stephen, RA
中科院分区：
文献类型：
--
作者：
Bromirski, PD;Duennebier, FK;Stephen, RA
Hawaii-2 天文台 (H2O) 远离海岸线和浅水区，是研究微震源区和传播的绝佳场所。在海洋钻探计划第 200 段期间，JOIDES Resolution 的官员进行了风和波浪测量，以便与在附近 H2O 收集的双频 (DF) 微震数据进行比较。 DF微震频带可分为短周期和长周期频带，分别为SPDF和LPDF。将船舶的天气日志与约0.20至0.45 Hz的SPDF频段的地震数据进行比较，显示地震振幅与风速和风向有很强的相关性，这意味着到达海底的能量是由海洋重力波局部产生的。近岸陆地地震台看到类似的 SPDF 频谱，也是由海风在当地产生的。在H2O处，SPDF微震振幅滞后于风速和风向的持续变化几个小时，并且滞后随着波周期的增加而增加。这种滞后可能与 DF 微震产生所需的相对海洋的发展有关。 H2O 上方的膨胀高度与 0.085 至 0.20 Hz 的 LPDF 频带的相关性通常很差，这意味着该能量的很大一部分源自遥远的位置。 H2O 地震数据与 NOAA 浮标数据、北太平洋后报波高数据以及大陆和岛屿台站地震数据的相关性确定了 LPDF 信号的可能源区。 H2O 的大部分 LPDF 能量似乎是由几乎同时影响长距离海岸线的高振幅风暴波产生的，当海浪从特定方向到达时，夏威夷群岛似乎是北太平洋 LPDF 能量的重要来源。当附近两个同时发生的风暴系统形成时，在大洋中部观测到的 H2O 最高水平出现在 SPDF 波段。在大陆站点没有观察到深水、海洋中部产生的 DF 微震，这表明这些信号的高度衰减。在近海岸地震台，SPDF 和 LPDF 微震级别通常由附近海岸线的本地产生主导。
The Hawaii-2 Observatory (H2O) is an excellent site for studying the source regions and propagation of microseisms since it is located far from shorelines and shallow water. During Leg 200 of the Ocean Drilling Program, the officers of the JOIDES Resolution took wind and wave measurements for comparison with double-frequency (DF) microseism data collected at nearby H2O. The DF microseism band can be divided into short-period and long-period bands, SPDF and LPDF, respectively. Comparison of the ship's weather log with the seismic data in the SPDF band from about 0.20 to 0.45 Hz shows a strong correlation of seismic amplitude with wind speed and direction, implying that the energy reaching the ocean floor is generated locally by ocean gravity waves. Nearshore land seismic stations see similar SPDF spectra, also generated locally by wind seas. At H2O, SPDF microseism amplitudes lag sustained changes in wind speed and direction by several hours, with the lag increasing with wave period. This lag may be associated with the time necessary for the development of opposing seas for DF microseism generation. Correlation of swell height above H2O with the LPDF band from 0.085 to 0.20 Hz is often poor, implying that a significant portion of this energy originates at distant locations. Correlation of the H2O seismic data with NOAA buoy data, with hindcast wave height data from the North Pacific, and with seismic data from mainland and island stations, defines likely source areas of the LPDF signals. Most of the LPDF energy at H2O appears to be generated by high-amplitude storm waves impacting long stretches of coastline nearly simultaneously, and the Hawaiian Islands appear to be a significant source of LPDF energy in the North Pacific when waves arrive from particular directions. The highest levels observed at mid-ocean site H2O occur in the SPDF band when two coincident nearby storm systems develop. Deep water, mid-ocean-generated DF microseisms are not observed at continental sites, indicating high attenuation of these signals. At near-coastal seismic stations, both SPDF and LPDF microseism levels are generally dominated by local generation at nearby shorelines.