A detailed receiver function image of the upper mantle discontinuities in the Japan subduction zone
A detailed receiver function image of the upper mantle discontinuities in the Japan subduction zone
复制标题
DOI：
10.1016/s0012-821x(00)00294-6
复制
发表时间：
2000-12
影响因子：
5.3
通讯作者：
X. Li;S. Sobolev;R. Kind;X. Yuan;C. Estabrook
中科院分区：
文献类型：
--
作者：
X. Li;S. Sobolev;R. Kind;X. Yuan;C. Estabrook
利用永久宽带台站远震记录的p - s转换相，对日本俯冲带活动大陆边缘及邻近地区30×20°大面积上地幔不连续面进行了成像。在其全球平均位置的±10公里范围内检测到410公里的不连续。在它的观测中，一个有趣的例外是135°E附近的一个缺口，非常接近410公里不连续面的板状穿透，并且在我们拥有相当高数据密度的区域。660公里的不连续面在两个地方直接被板块击中，深度达到700公里。这些数据通常与层析成像结果吻合良好。660 km的不连续凹陷和p -速度异常都表明板状体内部存在400 ~ 500 K的温度亏缺。然而，在中国东部的断层成像中，没有观测到660公里不连续面的向下弯曲。这表明该板块并没有冷却该地区660公里的不连续面。因此，保持平板平躺所需的正浮力不可能由尖晶石-钙钛矿相变的负克拉珀龙斜率提供。需要另一种机制，它可能是板冷核中的亚稳橄榄石。我们还在一些地震台站下约150公里处对板块较浅的部分进行了成像，可能是因为亚稳辉长岩在这个深度仍然存在，提供了足够的速度对比。在日本的一个火山区域下方150-200公里深处观测到一个强烈的负转换相。如果是真实的（仅在一个站点观察到），产生这种转化的区域，可能正好开始于板坯上方，将需要流体熔化。
We have imaged the upper mantle discontinuities in a 30×20° large region at the active continental margin of the Japan subduction zone and neighboring areas, using P-to-S converted phases from teleseismic records of permanent broadband stations. The 410 km discontinuity is detected within ±10 km of its global average position. An interesting exception in its observation is a gap near 135°E, very close to the slab penetration of the 410 km discontinuity and in an area where we have rather high data density. The 660 km discontinuity reaches 700 km depth at two places where it is hit directly by the slab. These data generally show good agreement with tomographic results. Both, the 660 km discontinuity depression and the P-velocity anomalies, suggest about 400–500 K temperature deficit within the slab. However, no downward bending of the 660 km discontinuity is observed in eastern China where the flat lying slab is imaged by tomography. This suggests that the slab does not cool the 660 km discontinuity in this region. Therefore the positive buoyancy required to keep the slab lying flat cannot have been provided by the negative Clapeyron slope of the spinel–perovskite phase transition. Another mechanism is needed, which could possibly be metastable olivine in the cold core of the slab. We have also imaged the shallower portion of the slab down to about 150 km underneath some seismic stations, likely because metastable gabbro is still existing to this depth providing a sufficient velocity contrast. A strong negative converted phase is observed at 150–200 km depth underneath a volcanic region in Japan. If real (observed at one station only), the zone which produces this conversion and which may begin exactly above the slab would require fluid-fed melting.