Map Sheet 48 (2025 update) - MMI from PGA and Epsilon (10% in 50 years)

The California Geological Survey (CGS) Map Sheet 48 (MS48) provides a depiction of expected ground shaking intensity from future earthquakes across the state. The shaking intensity is represented using the Modified Mercalli Intensity (MMI) scale, which describes the perceived earthquake shaking and correlates strongly with earthquake-induced damage. MS48 maps the level of shaking with a 2% probability of being exceeded in 50 years, equivalent to a 2,475-year average recurrence interval. In addition to MS48, eight interactive MMI hazard maps are presented. These include MMIs calculated using alternative methods. For each method, MMIs at two different hazard levels were presented: one with a 2% probability of being exceeded in 50 years (equivalent to 2,475-year recurrence interval) and the other with 10% probability of being exceeded in 50 years (equivalent to 475-year recurrence interval). The Arc GIS interface allows users to select any two MMI hazard maps to compare side by side. MMI values were calculated using several ground motion to intensity conversion equations (GMICEs). See the “Scientific Background” on MS48 webpage for detailed information. Due to software limitations, symbology cannot be added to this service. To match the symbology used in the MS48 MMI application, use the following configuration: Number of Classes: 7 Classes & Hex Codes: 4 - 5: #ffffbf 5 - 6: #f5f500 6 - 7: #f7ce00 7 - 8: #fa7d00 8 - 9: #fd2a00 9 - 10: #c70808 10 - 11: #8c0808加州地质调查局（California Geological Survey, CGS）第48号地图幅（MS48）呈现了加州全域未来地震可能引发的地面震动强度分布。该震动强度采用修订麦加利地震烈度（Modified Mercalli Intensity, MMI）量表进行表征，该量表可描述人们感知到的地震震动程度，且与地震诱发的破坏程度高度相关。MS48所映射的震动水平对应50年内超越概率为2%的地震危险性，等效于2475年的平均复发周期。除MS48之外，本次数据集还提供了八幅交互式MMI地震危险性地图，均通过不同计算方法生成。针对每种计算方法，均提供了两种不同危险性水平下的MMI结果：其一为50年内超越概率2%（对应平均复发周期2475年），其二为50年内超越概率10%（对应平均复发周期475年）。本数据集搭载ArcGIS界面，支持用户任选两幅MMI地震危险性地图进行并排对比。MMI数值通过多种地面运动-烈度转换方程（ground motion to intensity conversion equations, GMICEs）计算得到，详细信息可参见MS48网页上的“科学背景”板块。受限于软件限制，本服务无法添加符号系统。若需匹配MS48的MMI应用中所使用的符号系统，请采用如下配置：分类数：7类；十六进制颜色码：4-5级：#ffffbf；5-6级：#f5f500；6-7级：#f7ce00；7-8级：#fa7d00；8-9级：#fd2a00；9-10级：#c70808；10-11级：#8c0808