Malawi Seismogenic Source Model: v1.1

The Malawi Seismogenic Source Model (MSSM) is a geospatial database that documents the geometry, slip rate and seismogenic properties (ie earthquake magnitude and frequency) of active faults in Malawi. Each geospatial feature represents a potential earthquake rupture of 'source' and is classified based on its geometry into one of three types: section fault multi-fault Source types are mutually exclusice, and so if incorporated into a PSHA, they should be assigned relative weightings. The MSSM is the first seismogenic source database in central and northern Malawi, and represents an update of the South Malawi Seismogenic Source Database (SMSSD; Williams et al., 2021a) because it incorporates new active fault traces (Kolawole et al., 2021; Williams et al., 2021b; 2022 - MAFD), new geodetic data (Wedmore et al., 2021) and a statistical treatment of uncertainty, within a logic tree approach. The seismogenic sources in this model are adapted from the faults in the Malawi Active Fault Database (Williams et al., 2021b; 2022). Prior to publication please cite this database using the following two references: Williams, J. N., Wedmore, L. N .J., Fagereng, Å., Werner, M. J., Biggs, J., Mdala, H., Kolawole, F., Shillington, D. J., Dulanya, Z., Mphepo, F., Chindandali, P., Wright, L. J. M.., Scholz, C. A. Geological and geodetic constraints on the seismic hazard of Malawi's active faults: the Malawi Seismogenic Source Model (MSSM). <em>Manuscript submitted to Natural Hazards and Earth System Sciences</em> Williams, Jack N., Wedmore, Luke N. J., Fagereng, Åke, Werner, Maximilian J., Biggs, Juliet, Mdala, Hassan, Kolawole, Folarin, Shillington, Donna J., Dulanya, Zuze, Mphepo, Felix, Chindandali, Patrick R. N., Wright, Lachlan J. M., &amp; Scholz, Christopher A. (2021). Malawi Seismogenic Source Model [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5599616 Database Design and File Formats The MSSM is a geospatial database that consists of two separate components: A 3D geometrical model of fault seismogenic sources in Malawi The mapped trace of each source in a GIS vector format, with associated source attributes (Data Table). Each fault is associated with a source in the 3D geometrical model that is listed in a comma-separated-values (csv) file. The sections, faults and multi-faults that make up the individual seismogenic sources are described in separate geospatial files that describe the map-view geometry and metadata that control each sources earthquake magnitude and frequency for seismic hazard purposes. The sections, faults and multi-faults in this database are provided in a variety of GIS vector file formats. GeoJSON is the version of record, and any changes should be made in this version before they are converted to other file formats using the script in the repository that uses the GDAL tool ogr2ogr (the script is adapted from https://github.com/cossatot/central_am_carib_faults/blob/master/convert.sh - we thank Richard Styron for making this publicly available). The other versions available are ESRI ShapeFile, KML, GMT, and GeoPackage. List and brief description of the fault geometry, slip rate estimates and earthquake source attributes in the GIS vector format files that make up the MSSM. Attribuge Type Description Notes MSSM_ID integer Unique numerical reference ID for each seismic source ID 00-300 is section rupture<br> ID 300-500 is fault rupture<br> ID 600-700 is a multi-fault rupture name string Assigned based on previous mapping or local geographic feature.<br> <br> For sections and faults, the name of the fault (flt_name) and larger multi-fault (mflt_name) system they are hosted on are given respectively. basin string Basin that source is located within. Used in slip rate calculations class string intrarift or border fault length (L_s) real number straight-line distance in km between fault tips; sum of L_sec for segmented faults; sum of L_fault for multi-faults measured in km to 1 decimal place. Must be greater than 5 km (except for linking sections). area integer Calculated from L_s multiplied by Eq. 1 or based on fault truncation. measured in km² strike integer Azimuth of straigth line between the fault tips.<br> azimuth is &lt;180° Used as input for slip rate estimates in Eq. 2 dip_lower integer lower range of dip value When no previous measurements of dip are available, a nominal value of 45° is used. dip_int integer Intermediate dip value In the MSSM geometrical model, only the intermediate measurements is considered. When no previous measurements of are available, a nominal value of 53° is assigned.<br> <br> No dip is assigned for multi-fault sources, as different participating faults may have different dips. dip_upper integer Upper range of dip value When no previous measurements of dip are availabe, a nominal value of 65° is used. dip_dir string Dip direction: compass quadrant that the fault dips in. slip_type string Source kinematics (e.g. normal, thrust etc). All sources in the MSSM are assumed to be normal faults. slip_rate real number Mean value from repeating Eq. 2 in Monte Carlo simulations (see manuscript for details). In mm yr^-1. All sources in the MSSM are assumed to be normal so is equivalent to dip-slip rate.<br> <br> Reported to two significant figures. s_rate_err real number Slip rate error: 1σ error from Monte Carlo slip rate simlations. mag_lower real number Lower magnitude estimate.<br> <br> Calculated from Leonard (2010) scaling relationship (Eq. 4) for L_s or A_s, and using lower estimates of C₁ and C₂ constants in Leonard (2010). Reported to one decimal place. mag_med real number Mean magnitude estimate.<br> <br> Calculated from Leonard (2010) scaling relationship (Eq. 4) for L_s or A_s, and using mean estimates of C₁ and C₂ constants in Leonard (2010). Reported to one decimal place. mag_upper real number Upper magnitude estimate.<br> <br> Calculated from Leonard (2010) scaling relationship (Eq. 4) for L_s or A_s, and using upper estimates of C₁ and C₂ constants in Leonard (2010). Reported to one decimal place. ri_lower real number Lower recurrence interval estimate.<br> <br> Calculated as 1σ below the mean of the Monte Carlo simulations (assuming a log normal distribution). Reported to two significant figures. ri_med real number Mean recurrence interval.<br> <br> Mean value from log of recurrence interval Monte Carlo simulations. Reported to two significant figures. ri_upper real number Upper recurrence interval estimate.<br> <br> Calculated as 1σ above the mean of the Monte Carlo simulations (assuming a log normal distribution). Reported to two significant figures. MAFD_id list List of integers of ID of equivalent structures in the Malawi Active Fault Database Multi-fault sources have multiple ID's. Version Control This version is intended to be "Live" and as such we encourage edits of the GeoJSON file and the submission of pull requests. Please contact Jack Williams [e-mail] Luke Wedmore [e-mail] or Hassan Mdala [e-mail] for information, other requests or if you find any errors within the database. It is the intention that future versions of this database will include fault slip rates that have been determined from direct geological methods (e.g. offset stratigraphy that has been dated) rather than the systems based approach that is currently used. References Kolawole, F., Firkins, M. C., Al Wahaibi, T. S., Atekwana, E. A., &amp; Soreghan, M. J. (2021a). Rift Interaction Zones and the Stages of Rift Linkage in Active Segmented Continental Rift Systems. <em>Basin Research</em>. https://doi.org/10.1111/bre.12592 Leonard, M. (2010). Earthquake fault scaling: Self-consistent relating of rupture length, width, average displacement, and moment release. <em>Bulletin of the Seismological Society of America</em>, 100(5A), 1971-1988. https://doi.org/10.1785/0120090189 Wedmore, L. N. J., Biggs, J., Floyd, M., Fagereng, Å., Mdala, H., Chindandali, P. R. N., et al. (2021). Geodetic constraints on cratonic microplates and broad strain during rifting of thick Southern Africa lithosphere. <em>Geophysical Research Letters</em>. 48(17), e2021GL093785. https://doi.org/10.1029/2021GL093785 Williams, J. N., Mdala, H., Fagereng, Å., Wedmore, L. N. J., Biggs, J., Dulany, Z., et al. (2021). A systems-based approach to parameterise seismic hazard in regions with little historical or instrumental seismicity: Active fault and seismogenic source databases for southern Malawi. Solid Earth, 12(1), 187–217. https://doi.org/10.5194/se-12-187-2021 <strong>V1.1 Updates</strong> Updated seismic source files and model parameters. Changes are: Adding lower and upper dip estimates for sources (following a reviewer comment). This should be equivalent to Table 1 in the revised manuscript. Cleaning up the GIS files. In the old file there were some duplicate GIS features that are now removed Changing the name and acronyms from Malawi Seismogenic Source Database (MSSD) to Malawi Seismogenic Sources Model (MSSM). Included a basic Matlab script to plot the MSSM geometrical polygons

马拉维地震源模型（Malawi Seismogenic Source Model, MSSM）是一套地理空间数据库，用于记录马拉维境内活动断层的几何形态、滑动速率及地震成因属性（即地震震级与发生频率）。每个地理空间要素代表一个潜在的"震源"型地震破裂，并根据其几何形态划分为三类之一：分段断层、单断层及多断层。震源类型互斥，若将其纳入概率地震危险性分析（Probabilistic Seismic Hazard Analysis, PSHA），则需为其分配相对权重。

MSSM是马拉维中北部首个地震源数据库，同时也是对南马拉维地震源数据库（South Malawi Seismogenic Source Database, SMSSD; Williams et al., 2021a）的更新——该新版本纳入了新的活动断层迹线（Kolawole et al., 2021; Williams et al., 2021b; 2022 - MAFD）、新的大地测量数据（Wedmore et al., 2021），并采用逻辑树方法对不确定性进行统计处理。本模型中的地震源数据改编自马拉维活动断层数据库（Malawi Active Fault Database, Williams et al., 2021b; 2022）中的断层数据。正式发表前，请引用以下两篇文献：
1. Williams, J. N., Wedmore, L. N .J., Fagereng, Å., Werner, M. J., Biggs, J., Mdala, H., Kolawole, F., Shillington, D. J., Dulanya, Z., Mphepo, F., Chindandali, P., Wright, L. J. M.., Scholz, C. A. 马拉维活动断层地震危险性的地质与大地测量约束：马拉维地震源模型（MSSM）。*已投稿至《Natural Hazards and Earth System Sciences》的手稿*
2. Williams, Jack N., Wedmore, Luke N. J., Fagereng, Åke, Werner, Maximilian J., Biggs, Juliet, Mdala, Hassan, Kolawole, Folarin, Shillington, Donna J., Dulanya, Zuze, Mphepo, Felix, Chindandali, Patrick R. N., Wright, Lachlan J. M., & Scholz, Christopher A. (2021). 马拉维地震源模型[数据集]. Zenodo. https://doi.org/10.5281/zenodo.5599616

## 数据库设计与文件格式
MSSM是一套地理空间数据库，包含两个独立组成部分：
1. 马拉维境内断层地震源的三维几何模型
2. 采用GIS矢量格式存储的各震源映射迹线，附带相关震源属性（数据表）。

每个断层均对应三维几何模型中的一个震源，相关信息存储于逗号分隔值（comma-separated values, CSV）文件中。构成单个地震源的分段、单断层及多断层信息，存储于独立的地理空间文件中，这些文件描述了平面视图几何形态，以及用于控制各震源地震震级与发生频率（服务于地震危险性分析）的元数据。

本数据库中的分段、单断层及多断层数据以多种GIS矢量文件格式提供。GeoJSON为官方版本，所有修改均应在此版本中进行，随后可通过存储库中基于地理空间数据抽象库（Geospatial Data Abstraction Library, GDAL）工具ogr2ogr编写的脚本转换为其他格式（该脚本改编自https://github.com/cossatot/central_am_carib_faults/blob/master/convert.sh，在此感谢Richard Styron将其公开分享）。其他可用格式包括ESRI ShapeFile、KML、GMT及GeoPackage。

## 构成MSSM的GIS矢量格式文件中，断层几何、滑动速率估算值及地震源属性的列表与简要说明
### 属性详情
MSSM编号（MSSM_ID）：整数型，每个地震源的唯一数字参考ID。其中ID 00-300对应分段破裂，ID 300-500对应单断层破裂，ID 600-700对应多断层破裂。
名称（name）：字符串型，基于既往制图或当地地理实体命名。对于分段与单断层，分别给出其所属断层（flt_name）及更大规模多断层系统（mflt_name）的名称。
盆地（basin）：字符串型，震源所在的盆地，用于滑动速率计算。
类型（class）：字符串型，裂谷内部断层或边界断层。
长度（Lₛ）：实数型，断层端点间的直线距离，单位为km，保留1位小数。对于分段断层，为各分段长度（L_sec）之和；对于多断层，为各单断层长度（L_fault）之和。需大于5km（链接分段除外）。
面积（Aₛ）：整数型，由Lₛ乘以公式1计算得到，或基于断层截断情况确定，单位为km²。
走向（strike）：整数型，断层端点间直线的方位角，方位角小于180°，用作公式2中滑动速率估算的输入参数。
下倾角（dip_lower）：整数型，倾角取值下限。若无既往倾角测量数据，则采用默认值45°。
中间倾角（dip_int）：整数型，倾角中间值。在MSSM几何模型中仅采用中间倾角值。若无既往倾角测量数据，则采用默认值53°。多断层震源无倾角赋值，因为其包含的各参与断层倾角可能存在差异。
上倾角（dip_upper）：整数型，倾角取值上限。若无既往倾角测量数据，则采用默认值65°。
倾向（dip_dir）：字符串型，断层倾角的罗盘象限方向。
滑动类型（slip_type）：震源运动学属性（例如正断层、逆断层等）。MSSM中所有震源均假设为正断层。
滑动速率（slip_rate）：实数型，蒙特卡洛模拟中重复公式2得到的平均值，单位为mm yr⁻¹。由于MSSM中所有震源均为正断层，因此该值等价于倾滑速率。保留两位有效数字。
滑动速率误差（s_rate_err）：实数型，蒙特卡洛滑动速率模拟得到的1σ误差。
下限震级（mag_lower）：实数型，下限震级估算值。基于Leonard (2010) 的震级缩放关系（公式4），利用Lₛ或Aₛ计算得到，同时采用Leonard (2010) 中C₁与C₂常数的下限估算值。保留1位小数。
平均震级（mag_med）：实数型，平均震级估算值。基于Leonard (2010) 的震级缩放关系（公式4），利用Lₛ或Aₛ计算得到，同时采用Leonard (2010) 中C₁与C₂常数的平均估算值。保留1位小数。
上限震级（mag_upper）：实数型，上限震级估算值。基于Leonard (2010) 的震级缩放关系（公式4），利用Lₛ或Aₛ计算得到，同时采用Leonard (2010) 中C₁与C₂常数的上限估算值。保留1位小数。
下限复发间隔（ri_lower）：实数型，下限复发间隔估算值。基于对数正态分布假设，为蒙特卡洛模拟复发间隔均值下方1σ处的值。保留两位有效数字。
平均复发间隔（ri_med）：实数型，平均复发间隔。为蒙特卡洛模拟复发间隔对数的均值。保留两位有效数字。
上限复发间隔（ri_upper）：实数型，上限复发间隔估算值。基于对数正态分布假设，为蒙特卡洛模拟复发间隔均值上方1σ处的值。保留两位有效数字。
MAFD编号（MAFD_id）：列表型，马拉维活动断层数据库中对应构造的ID整数列表。多断层震源可包含多个ID。

## 版本控制
本版本为"动态"版本，我们鼓励对GeoJSON文件进行编辑并提交拉取请求。如需咨询、其他请求或发现数据库中的错误，请联系Jack Williams（[e-mail]）、Luke Wedmore（[e-mail]）或Hassan Mdala（[e-mail]）。

未来版本的数据库计划纳入通过直接地质方法（例如已定年的偏移地层）确定的断层滑动速率，而非当前采用的基于系统的参数化方法。

## 参考文献
Kolawole, F., Firkins, M. C., Al Wahaibi, T. S., Atekwana, E. A., & Soreghan, M. J. (2021a). 裂谷相互作用带与主动分段大陆裂谷系统的裂谷连接阶段。*Basin Research*. https://doi.org/10.1111/bre.12592
Leonard, M. (2010). 地震断层缩放：破裂长度、宽度、平均位移与矩释放的自洽关系。*Bulletin of the Seismological Society of America*, 100(5A), 1971-1988. https://doi.org/10.1785/0120090189
Wedmore, L. N. J., Biggs, J., Floyd, M., Fagereng, Å., Mdala, H., Chindandali, P. R. N., et al. (2021). 非洲南部厚岩石圈裂谷作用期间克拉通微板块与宽应变的大地测量约束。*Geophysical Research Letters*. 48(17), e2021GL093785. https://doi.org/10.1029/2021GL093785
Williams, J. N., Mdala, H., Fagereng, Å., Wedmore, L. N. J., Biggs, J., Dulany, Z., et al. (2021). 历史与仪器地震记录匮乏地区地震危险性参数化的系统方法：南马拉维活动断层与地震源数据库。*Solid Earth*, 12(1), 187–217. https://doi.org/10.5194/se-12-187-2021

## V1.1版本更新
本次更新内容如下：
1. 为震源添加上下倾角估算值（回应审稿人意见），对应修订后手稿中的表1；
2. 清理GIS文件，移除旧文件中存在的部分重复地理空间要素；
3. 将名称与缩写从马拉维地震源数据库（Malawi Seismogenic Source Database, MSSD）更改为马拉维地震源模型（Malawi Seismogenic Sources Model, MSSM）；
4. 新增用于绘制MSSM几何多边形的基础Matlab脚本。