由政府等权威机构监测、采集地震灾情信息后,向公众通告并指导公众采取应对措施,是当前防震减灾过程中的主要信息流通模式。然而,在这种信息单向流动模式中,公众缺少主动查询获取和反馈灾情信息的渠道,不利于防震减灾和灾后恢复重建。本文针对现有地震信息系统在公众信息服务方面的不足,首先分析了公众参与式地理信息系统(Public Participation Geographic Information System,PPGIS)的特点及应用,从地震灾害管理的整个周期出发,将地震灾害信息分为4大类,进行平台数据库和功能设计;随后,探讨了基于PPGIS的大众地震信息服务平台,在公众主动获取多源地震灾情和地震知识、提交和反馈灾情信息与救助需求,以及参与灾后重建等方面的作用,并分析了该平台中用户数据质量及质量控制流程;最后,在此基础上,设计并实现了基于PPGIS的大众地震灾情信息服务平台原型系统,为解决公众地震灾情获取和反馈提供了可行性方案,为类似系统的设计与实现提供了参考。
The nomaal moveout correction is important to long-offset observations, especially deep layers. For isotropic media, the conventional two-term approximation of the normal moveout function assumes a small offset-to-depth ratio and thus fails at large offset-to-depth ratios. We approximate the long-offset moveout using the Pade approximation. This method is superior to typical methods and flattens the seismic gathers over a wide range of offsets in multilayered media. For a four-layer model, traditional methods show traveltime errors of about 5 ms for offset-to-depth ratio of 2 and greater than 10 ms for offset-to-depth ratio of 3; in contrast, the maximum traveltime error for the [3, 3]-order Pade approximation is no more than 5 ms at offset-to-depth ratio of 3. For the Cooper Basin model, the maximum oft＇set-to-depth ratio for the [3, 3]-order Pade approximation is typically double of those in typical methods. The [7, 7]-order Pade approximation performs better than the [3.3]-order Pade armroximation.
