We study the effect of natural disasters on port level exports. We model the interaction between firms and ports to study how strongly exports from one port are affected by changes in the cost of exporting at neighboring ports. We extend the standard trade model with heterogeneous firms to a multiple port structure where exporting is subject to port specific local transportation costs, port specific fixed export costs and international bilateral trade costs. We show that gravity distortion due to firm heterogeneity is conditional on the comparative advantage at the port level and resulting substitution of exports across ports. We present evidence of the substitution effect using the 2011 Great East Japan Earthquake, indicating that at least 40% of exports was substituted to other ports following the disaster. The substitution effects is strongest in technology intensive product categories, which suggests an interaction between supply chains and domestic trade costs.

中文翻译：

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自然灾害和贸易：港口替代的缓解影响

我们研究了自然灾害对港口出口的影响。我们对企业和港口之间的相互作用进行建模，以研究一个港口的出口受邻近港口出口成本变化的影响有多大。我们将具有异构公司的标准贸易模型扩展到多港口结构，其中出口受港口特定的本地运输成本、港口特定的固定出口成本和国际双边贸易成本的影响。我们表明，由于企业异质性导致的重力扭曲取决于港口层面的比较优势以及由此产生的跨港口出口替代。我们使用 2011 年东日本大地震提供替代效应的证据，表明至少 40% 的出口在灾难发生后被替代到其他港口。