在地幔中发生中等深度地震的周期性剪切加热机制
1Department of Earth and Environmental Sciences, Columbia University, Lamont Doherty Earth Observatory, Palisades, New York 10964, USA. peterk@ldeo.columbia.edu
Nature
|April 13, 2007
概括
中等深度地震源于局部粘性爬行,而不仅仅是脱水. 这种新模型解释了俯冲区以下的地震活动,揭示了准周期性的不稳定周期.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 构造学 构造学 构造学 构造学
背景情况:
- 中等深度的地震发生在柔软-柔性过渡下方的俯冲区.
- 现有的模型表明热或脱水机制,但这些对于一些地震地点是不够的.
- 在这些深度的高压使得摩擦故障不太可能.
研究的目的:
- 建议和建模用于中度深度地震的替代机制.
- 为了解释发生在含水矿物质存在的深度以下的地震活动.
主要方法:
- 在粗粒度弹性半空间内的细粒度剪切区域的数值建模.
- 利用奥利文流动规律并模拟剪切加热效应.
- 结合初始温度 (600-800°C) 和背景应变速率 (10−1210−15秒−1).
主要成果:
- 由于剪切加热,局部粘性爬行迅速开始,增加了拉伸速率和温度.
- 应变速率超过1s-1和温度达到1,400°C,然后是应力下降.
- 这个过程导致在持续的远场变形下,半周期性的地震不稳定.
结论:
- 在细粒度剪切区域的粘性爬行为中等深度地震提供了可行的机制.
- 这种机制解释了发生在比脱水可能更深处的地震.
- 该模型预测这些地震事件的周期性.
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