Implementation and future challenges of seismotectonic mapping system for earthquake emergency response

Earthquake emergency response maps represent a set of geographical maps related to the seismic activity, geological tectonic background, assessment of economy and population losses, secondary disaster probability, as well as other information for emergency response and rescue. It requires producing these kinds of maps as quickly as possible after an earthquake. The seismotectonic map is one of the most important maps for earthquake emergency response. In this study, we developed an earthquake emergency response system to produce the map automatically. This paper introduces a intelligent system framework using spatial analysis, version management and web communication technology for emergency response, data maintenance, remote map revision, version management and statistics, which is not discussed in previous studies. The system based on MySQL, ArcGIS platform, python, and curl. It can detect the earthquake fast report proactive. When capturing the official report, it activated the response function module. The system achieved the first version mapping, fault data pushing, and earthquake catalogue updating by data-driven method automatically and rapidly. The mapping process can be divided into map layout and expert knowledge. The expert knowledge part can be divided into a geography map and explanatory note. The system performed well on the map layout and geography map. The explanatory note in the map, which introduces regional tectonics and expert knowledge, can provide the nearest fault’s name, active age, and feature in the first version. Experts need to produce the second version manually. The fault data of 5°×5°area centred on the main shock is clipped and sent to a specified mailbox. The system added the earthquake parameters to the database. The result shows that this system finished these work well automatically and reduce the responds time and data maintenance time. If the earthquake causes serious calamity, seismogeology experts need to collect, summarize and analyse literature, document, and other information for successor versions and even predicting aftershock and disaster. It is practically needed to build a more intelligent and efficient system to produce a successor version of the map and push more knowledge in the future. The challenge in the future is to develop a more intelligent system to self-explain the seismotectonic map and push expert knowledge. This goal can only be achieved by processing expert knowledge data like regional lithology, tectonic structure, paleo earthquake, and historical earthquake in the database layer, data access layer, and business logic layer of the system.


Introduction
Earthquake is one kind of nature disaster with powerful destructive power. Seismic activity and damage have certain pattern. Is the strong earthquake main shock or front shock? Will more and stronger earthquake happen after the shock? What kind of secondary disaster will happen? These questions are relative to the seismic activity pattern, geological structure, disaster background, social economy, population distribution, secondary disaster probability and other factors in the region. For disaster reduction and relief, government needs information as soon as possible after a strong earthquake. A set of thematic maps is a visual and important form to show these information and disaster-inducing factors. These maps include knowledge-based maps like seismotectonic map and crustal movement velocity map, and inversion maps like focal mechanism solution and aftershocks distribution map. The seismotectonic map visually show the regional seismotectonic background and the possible seismogenic fault. It is required to output seismotectonic map in 2 hours after strong earthquake (M≥5.0) under the demand of earthquake emergency response system. It takes about 1 hour for cartography, data slicing, data packing, validation, and data pushing. Considering that cartographer is not always sitting in front of the computer, the response time of 2 hours is just enough. However, the work is not efficient enough.
Auto mapping triggered by earthquake rapid report is an efficient technique for emergency response. U.S. Geological Survey (USGS)and China Earthquake Networks Center(CENC) both have rapid emergency respond system to produce seismic epicenter distribution map automatically. The rapid mapping method and technique is also used in earthquake disaster loss assessment, shake map, building damage estimation, casualty estimation, and landslide prediction [1][2][3][4][5][6][7][8]. Previous researches focused on the parameter calculation algorithm, technology platform or implementation. The rapid mapping system in this paper is not only focusing on auto-mapping, but also on automatically data updating, remote map updating and pushing. This paper mainly studies on function, framework, advantages and prospects of auto seismotectonic mapping system for earthquake emergency response. This study proves that data updates, version management, web communication and spatial analysis are also important in response efficiency, system maintenance cost, map revision and production updates. It is rarely studied in previous studies.

Platform
The emergency system in this paper based on ArcGIS and developed using ArcObjects, Python and curl. Mapping data is stored in ArcGIS format. System data like user information is managed in MySQL. ArcGIS is a GIS platform which has brilliant ability in mapping and GIS data management. ArcGIS can build data into a map with independently-developed technology of symbol library, label engine and map representation. The user-designed map layout, symbol, label etc, can be store in map template. The map template can be used to make a new map with same design if the mapping data schema is the same and only the data content is changed. A new map with same style and layout view can be finished only by changing data source. ArcGIS 10 and later version also provides data-driven mapping tool. Based on the configuration of map template, mapping data and a set of mapping area, the tool can move the output window and make a set of thematic maps in the same style. When strong earthquake occur, emergency personnel use prepared seismotectonic data and geography data to make a seismotectonic map by changing main sock location and mapping area. The map produced every 3 time must be in the same layout, symbol and style. ArcGIS map template and data-driven mapping tool is suitable for this application scenario.

Workflow
Once China National Seismic Network monitor a strong earthquake, it rapidly report a message automatically. After a few minutes, CENC corrects the earthquake parameter error and publishes a formal report. The rapid report and formal report are published and pushed in many ways. For example, WeChat Official Account, Sina Weibo, E-mail, phone message and App. The response team members must make thematic maps once received the formal report. The seismotectonic map was made by prepared data and map template in an area of about (3~5) °×(3~5) °centred on the earthquake. The nearest fault's name, feature and active age is also described in the map. This first version can help geological expert to make a preliminary estimate of seismogenic structure. In the circumstances of having new explanation of seismogenic structure, fault data or relocated after shock, a newer version map must be make again. Emergency team member need to send it to experts and specific person. In order to avoid errors caused by negligence, every version must be checked again before formally reporting to superiors.
The current version of seismotectonic auto-mapping system achieved some work of the emergency response described in previous paragraph. In addition, it can record the product version and output statistical products report. The system includes three work flows as follow: 1) auto-mapping of the first version, 2) remote modifying the description text on the map, 3) recording and calculating the productions. When receiving the earthquake report, remote request of modifying descriptor or statistic, the system deal the message with specific modules as shown in figure 1.These modules and functions in figure 1 will introduce in next section. The system automatically detects earthquake report regularly. Once the conditions for producing emergency maps are met (M≥5.0), the system will automatically produce the first version of seismotectonic map based on pre-set map template. After receiving a request of modifying the description text of the map, the system will automatically produce the subsequent version of the  2).The description text includes earthquake's location and magnitude, and nearest fault's name, direction, active age and distance from the epicentre.

Product distribution.
The system's production includes JPG image version of the map, ArcGIS mxd file, shapefile format vector sections of faults in the 5°×5° region centred on the earthquake, earthquake parameter file, shapefile format vector file of earthquake catalogue updated by the system within one year, and statistical report of map products. All these productions can be distributed and pushed to certain person. This module has functions of data slicing, data packing and data pushing to certain mail.

Data updates.
When the system produces the first version, the earthquake's parameter is added to earthquake catalogue. This work is automatically also. So far, this module can add the earthquake (M≥5.0) automatically to the database.

Version management.
The system can automatically tab the map product with version number and record the production time. Therefore, the system can provide the version information of the specified map.

Product statistics.
This module can output a statistic report of earthquake parameters, product version and time.

Data
The data layers of seismotectonic map include main shock, fault, quaternary, earthquake catalogues, river system, administrative boundary and resident point. Main shock data is auto-generated based on the parameters fetched from CENC's formal earthquake report. Fault data is an updated version of fault in "Seismotectonic Map in China and its Adjacent Regions (in Chinese)" [9], which scale is 1:4 000 000. The older version was reconstructed using Python and PyShp [10].Then it was updated based on an active fault-surveying project from 2009 to 2016. In this project, nearly ~100 active faults were surveyed and mapped in the scale of 1:50 000. These data from the project are more spatially accurate and more reliable than the 1:4 000 000 one. This data is published on the website now. (http://www.neotectonics.cn/arcgis/apps/webappviewer/index.html?id=3c0d8234c1dc43eaa0bec3ea03 bb00bc) The earthquake data is the official earthquake catalogue published by CENC. River system, administrative boundary and resident point data are official data of National Geomatics Center of China (NGCC) on the scale of millions. The sources of mapping data is reliable. It ensures the integrity and accuracy of the final product.

System performance
The seismotectonic auto-mapping system was launched in September 2019 to produce real-time emergency response map for strong earthquake (M≥5.0). After three version from the beginning, the system have achieved all the works in section 2.3, output 51 map procucts, finished 36 times of data slicing and packing, and distributed products 51 times. There are only JPG format map files in the first 16 times, which were send to a specific QQ group. In the last 36 times, the system pushed different products in groups to specific users' mailbox. Figure 4 and figure 5 shows the ArcMap document files and JPG image files of seismotectonics map from September to December 2019 for strong earthquake(M≥5.0) occurred in China. Figure 6 shows that the system distributed products through QQ and e-mail.  The emergency response map was finished at 2:16. Slice vector fault data has been prepared and packed at 2:17. User received products at 2:19 via email. The system response to these two earthquake and finished mapping and distribution within 15 minutes. It works more efficient than operation and mapping by hand. The auto-mapping also avoid the manual errors when modifying the map name, legend, explanatory text and other contents in the map.

Discussion and conclusion
Since the three version of the system launched, it auto-complete earthquake response for 11 times ( Table 1). The average response time is 10.63 minutes. The shortest time is 8 minutes, while the longest time is 15 minutes. This response time is calculated form main shock happened to the time when the system has completed data distribution. (The response time mentioned below is as the same.) The system has completed emergency map-making, fault data slicing, earthquake data appending (M≥5.0), data packing and distribution. Suppose cartographer is sitting in front of computer all the time. The time of receiving formal report within 10 minutes after earthquake happened. When received the formal earthquake report, cartographer can respond immediately. It will take 30~40 minutes to output map, slice data, pack data and distribute products. After emergency response, it will take about 15 minutes to add new earthquake data to database. All these will take more than 1hour.Statistical results shows that the system reduced the response time to an average of about 10 minutes with a fast and efficient response ability.
Three factors decides the response time: CENC's response time to release formal earthquake report, the interval time of fetching the CENC's report, and the run time of mapping, packing and distribution. The CENC release formal earthquake report after main shock in 5 to 10 minutes through Sina Weibo. The interval time to refresh Weibo is limited. So the emergency mapping system fetched the report every 3~5 minutes one time. The run time of mapping, packing and distribution is about 3 minutes, which is relatively fixed. Because of the first two factors, the whole response time varies with them. If the CENC's response time is shorter and fetching time is near report releasing time, the response time is shorter.