Development of a Web-GIS based Decision Support System for earthquake warning service in Vietnam

Vietnam Journal of Earth Sciences, 40(3), 193-206, Doi: 10.15625/0866-7187/40/3/12638 193 (VAST) Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences Development of a Web-GIS based Decision Support System for earthquake warning service in Vietnam Nguyen Hong Phuong1, 2, 3*, Nguyen Ta Nam1, Pham The Truyen1, 2 1Institute of Geophysics (VAST), Hanoi, Vietnam 2Graduate University of Science and Technology(VAST), Hanoi, Vietnam 3IRD, Sorbonne Universités, UPMC Univ Paris 06, Unité Mixte Internationale de Modélisation Mathé- matique et Informatiques des Systèmes Complexes (UMMISCO)32 venue Henri Varagnat, 93143 Bondy Cedex, France Received 03 February 2018; Received in revised form 09 April 2018; Accepted 30 May 2018 ABSTRACT This paper describes the development of a Decision support system (DSS) for earthquake warning service in Vietnam using Web GIS technology. The system consists of two main components: (1) an on-line database of earth- quakes recorded from the national seismic network of Vietnam, and (2) a set of tools for rapid seismic hazard as- sessment. Using an on-line earthquake database, the system allows creating a shake map caused by a newly recorded earthquake. In addition, the Web GIS environment allows any user, including non-professional to get useful infor- mation about a just-occurred event and the possible impact caused by the earthquake shortly after its occurrence. A fault-source model developed for Vietnam was used as a part of the hazard calculation and mapping procedure. All information and results obtained from the system are automatically included in the earthquake bulletins, which will be disseminate national wide afterward by the Vietnam earthquake information and tsunami warning Center. The shake maps produced by the DSS in terms of both Peak Ground Acceleration and intensity values are rapidly available via the Web and can be used for emergency response, public information, loss estimation, earthquake plan- ning, and post-earthquake engineering and scientific analyses. Application of the on-line decision support system in earthquake warning service can mitigate the earthquake risk and reduce the losses and damages due to earthquakes in Vietnam in future. Keywords: Web-GIS; decision support system; earthquake hazard; RARE. ©2018 Vietnam Academy of Science and Technology 1. Introduction* Earthquakes cause the damages on the Earth’s surface. The severity of damage in terms of casualties and loss of properties caused by an earthquake in the region near ep- icenter greatly depends on its focal depth and *Corresponding author, Email: phuong.dongdat@gmail.com magnitude. Despite of the fact that prediction of earthquake occurrence time is inherently impossible, the fast detection and early warn- ing of an earthquake’s parameters can help considerably to reduce the casualties and loss- es in the epicenter region. The Institute of Geophysics (IGP) within the Vietnam Academy of Science and Tech- nology (VAST) is operating the national Nguyen Hong Phuong, et al./Vietnam Journal of Earth Sciences 40 (2018) 194 seismic network and has been given the re- sponsibility for issuing earthquake infor- mation throughout the territory of Vietnam and adjacent sea areas in order to reduce the impact of this natural disaster. For earthquake detection, the waveforms recorded from the seismic stations throughout the country are displayed on the large screens of the Earth- quake Information and Tsunami Warning Center at IGP. Seconds or minutes after oc- currence of an earthquake, its main parame- ters such as the occurrence time, coordinates of epicenter, focal depth and magnitude are defined both manually and automatically by specialized software. As the time for saving lives and properties after earthquakes is counted in minutes, it is important to reduce the time of earthquake data processing from the moment of earthquake detection to the moment of issuing warning. The most com- mon information available immediately fol- lowing damaging earthquakes are traditionally their magnitude and epicenter location. How- ever, the damage pattern is not a simple func- tion of these two parameters alone, and more detailed information is required to properly evaluate the situation. This paper describes the development of a Decision Support System (DSS) for earthquake warning service in Vietnam. The two main functions of the system include Rapid Assess- ment of Real-time Earthquakes (RARE) and issuing earthquake bulletins. The DSS aims to enhance the capability of the national earth- quake warning service in order to mitigate and reduce the earthquake risk in the entire territory of Vietnam and adjacent sea areas. 2. Technology basis To develop the Decision Support System for on-line earthquake warning, a Web-GIS technology has been applied, using the open source programs and libraries that widely pro- vided in the internet. The interface of the De- cision Support System for on-line earthquake warning (below referred as DSS), which was designed on the basis of HTML, CSS and the PHP programming language, was used for in- teraction between users and a PostgreSQL da- tabase. The system’s most important GIS component is displayed in the form of a map containing three main layers namely the base map of the study area covering the whole ter- ritory of Vietnam and the East Vietnam sea; the seismically active faults systems in the study area, and epicenters of earthquakes in- strumentally recorded in the study area. The DSS’s map layers, created by the Mapserver, Openlayer and PostGIS applica- tions, providing a flexible and effective envi- ronment for users to work with spatial data. In addition, some other functions have been de- veloped to enhance the DSS’s security and ef- ficiency as the user permission or the switch between Vietnamese and English languages. All programs are working in the Window en- vironment to ensure the compatibility and sta- bility of the system. Working in the Web en- vironment, the DSS can be used by any user with access to the internet and with such pop- ular web browsers as Firefox, Chrome, Knock Knock, etc. Figure 1 illustrates the DSS’s user inter- face as it will be linked to the website of the Institute of Geophysics (IGP). The upper part shows logo and address of the Earthquake In- formation and Tsunami Warning Center, IGP. The upper right buttons allow users to log in the system and choose working language. The tabs in the lower part of the display can be used for accessing to different components of the system. From left to right, the names and contents of the tabs are described below. (i) The “Homepage” tab contains the intro- ductory information about the Earthquake In- formation and Tsunami Warning Center, IGP. (ii) The “Earthquake Bulletins” allows to display the bulletins of the most recent earth- quakes, issued by the Earthquake Information and Tsunami Warning Center, IGP. (iii) The “Seismicity map” tab gives ac- cess to a seismicity map, showing distribution of epicenters of the most recent earthquakes, instrumentally recorded in the territory of Vietnam and adjacent sea areas. Vietnam Journal of Earth Sciences, 40(3), 193-206 195 (iv) The “Earthquake Database” tab gives access to a database of the most recent earth- quakes recorded in in the territory of Vietnam and adjacent sea areas. The database is regu- larly updated at the IGP. (v) The “Earthquake Hazard” tab pro- vides a toolset for rapid assessment of real- time earthquakes (RARE), which can be used for calculating and displaying a shake map caused by a rea-time earthquake. The hazard information taken from the shake map then will be automatically added into the earth- quake bulletin. To fulfill earthquake warning task, the most important role in the DSS play the on- line earthquake database and the toolset for rapid assessment of seismic hazard from a re- al-time earthquake. Figure 1. User interface of the Decision Support System for on-line earthquake warning 3. On-line database of recent earthquakes in Vietnam An on-line database is designed and in- cluded into the DSS to store the most recent earthquakes occurred in the territory of Vietnam and the adjacent sea areas. All of these events were recorded by the national and local seismic networks of Vietnam, oper- ated by the Institute of Geophysics. The pa- rameters of all recorded earthquakes are in- formed in the IGP website and in the earth- quake bulletins issued and disseminated na- tional wide by IGP in case if the magnitude Nguyen Hong Phuong, et al./Vietnam Journal of Earth Sciences 40 (2018) 196 exceeds M3.5. The users can access to work with the on-line database of earthquakes in Vietnam by clicking on one of the “Seismicity map” and “Earthquake database” tabs in the DSS’s interface. After clicking on the “Seismicity map” tab, a map showing distribution of epicenters of the earthquakes, being stored in the on-line database will appear (Figure 1). On the map, the epicenter of the last recorded earthquake is denoted by a big star to distinguish with the others, which are denoted by the circles. The sizes of the circles are proportional to the magnitudes of earthquakes they represent. The seismicity map gives a visualization of con- temporary seismic activity in the territory of Vietnam and adjacent sea area. The users can click on each epicenter on the map to query the parameters of the event, such as occur- rence time, epicenter’s coordinates, the focal depth, magnitude and the name of the place where earthquake occurred. The users can al- so retrieve and display the issued bulletin of each event. In addition, the tools located at the lower part of the interface allow searching earthquakes from the on-line database accord- ing to such various criteria as magnitude, depth, year of occurrence and place name. The sought data, which satisfies the sort crite- ria, will be displayed on the map. The “Earthquake database” tab gives ac- cess to the on-line database of recent earth- quakes in Vietnam. Here, the users can browse a catalog of the most recent earth- quakes and work with the database by several manipulations such as update, edit, and delete events (Figure 2). Figure 3 illustrates a tool for inputting the parameters of a newly rec- orded earthquake into database. Once the user has input the earthquake parameters and clicked “Submit” button, a message will ap- pear asking the user to confirm the location of the new earthquake before it will be stored in the database. As the new earthquake is added into the catalog, its epicenter will also appear on the seismicity map (see Figure 1). Figure 2. Catalog of earthquakes, stored in the on-line database of recent earthquakes in Vietnam Vietnam Journal of Earth Sciences, 40(3), 193-206 197 Figure 3. Input window for updating a new earthquake into the on-line database The most important function of the on-line earthquakes database is to provide input pa- rameters for the rapid assessment of a real time earthquake tool (RARE). The develop- ment and application of the RARE will be de- scribed in details in the following paragraphs of the paper. 4. Development of an on-line tool for sce- nario based seismic hazard assessment 4.1. Seismic source modeling The quantitative seismic hazard assessment is usually based on pre-developed source models, which simulate the process of energy release and seismic wave propagation of an earthquake from source to site. The seismic hazard models allow to calculate hazard at a given point and then to construct the hazard map for the entire study area. Such seismic hazard models were first de- veloped and used by Cornell (1968) and Milne and Davenport (1969). In these models, it is assumed that the total energy released by earthquakes radiated from the focus of the earthquake, and therefore may be called “point-source models”. The application of the point-source models would not be accurate in case of major earthquakes, when total energy released is distributed along the rupture zone that could be several tens or hundreds kilome- ters long or when the site is located very close to the fault. In general, the rupture length is a significant parameter in the determination of seismic hazard, and neglecting its effect would tend to underestimate the real risk to large-magnitude earthquakes. To overcome the disadvantages of point-source models, Der Kiureghian and Ang (1977) at the same time with Douglas and Ryall (1977), proposed a fault-source model, which is based on the as- sumption that an earthquake originates at the focus and propagates as an intermittent series of fault ruptures or slips in the rupture zone of the Earth’s crust, and that the maximum inten- sity of ground shaking at a site is determined by the slip that is closest to the site. However, the modeling of seismic sources has only be- come effective with application of GIS tech- nology. Nguyen Hong Phuong, et al./Vietnam Journal of Earth Sciences 40 (2018) 198 In Vietnam, GIS technology has been ap- plied in deterministic seismic hazard assess- ment since beginning of the 21st century. With assumption that an earthquake originates on a rupture of an active fault, a fault source model was developed for Vietnam using a database of 46 seismically active fault systems in the territory of Vietnam and adjacent sea area (Bui Van Duan et al., 2017). The fault sys- tems are grouped in two ranks, depending on their depth of active layers and magnitude thresholds and digitized in a GIS environ- ment, then linked with their attribute data. There are two types of fault attribute data stored in the database. The first type is the de- scriptive information, including fault name, fault rank, type of faulting, main direction, to- tal length, etc. More important attribute type is the fault parameters, which can be used di- rectly to the hazard calculation as maximum moment magnitude, surface and subsurface rupture sizes, fault plan solutions, etc. For each fault system, the Wells and Cop- persmith (1994) empirical relationship be- tween earthquake magnitude M and rupture length L has been applied: Log10(L) = a + b* M (1) where L is the rupture length (km) and M is the moment magnitude of the earthquake; a and b are regression coefficients, determined for different types of faults and given in Table 1. Table 1. Regression coefficients of fault rupture rela- tionship of Wells and Coppersmith (1994) Rupture type Fault type a b Surface Strike slip Reverse All -3,55 -2,86 -3,22 0,74 0,63 0,69 Subsurface Strike slip Reverse All -2,57 -2,42 -2,44 0,62 0,58 0,59 4.2. Attenuation models When an earthquake occurs, the energy ra- diates from the source will impact the Earth’s surface in terms of ground shaking. Relation- ship between the ground motion parameters Y, the earthquake magnitude M and the focal distance R, also known as the attenuation equation, can be express as follows: 𝑌𝑌 = 𝑐𝑐1 exp(𝑐𝑐2𝑀𝑀)𝑅𝑅𝑐𝑐3 (2) where Y is one of the peak ground motion values (acceleration, velocity, or displace- ment), c1, c2 and c3 are spatial dependent con- stants. In case of a fault source, R indicates the distance from fault to site. The establishment of an attenuation equa- tion to be applied for a study region is im- portant and usually considered as a separate stage in the whole seismic hazard assessment procedure. Vietnam, however, as many other low-seismicity countries of the World, is al- ways facing the problem in developing an at- tenuation law aplicable for the country. Alt- hough several large earthquakes have oc- curred within the territory of Vietnam, there were no strong ground motion data available for the country untill the year 2000, where the first strong ground motion record of the coun- try was obtained from a M5.0 event. Due to the lack of strong ground motion data of the strong earthquakes, for a long time no local attenuation equations have been developed for Vietnam. There have been attempts to develop atten- uation equations for Vietnam. Xuyen and Thanh (1999) proposed an empirical equation developed from the isoseismal maps, collected during field investigations of different earth- quakes in Vietnam. However, the reliability of this equation is questionable as the field in- vestigation data does not reflect the direct re- lationship between earthquake magnitude and the ground shaking parameters. In 2011, two groups of authors independently published the attenuation equations developed for Vietnam (Minh et al., 2012, Tran and Kiyomiya, 2012). However, for the first study, the earthquake data used has been collected within a small area in North Vietnam and all of them have medium magnitudes (Minh et al., 2012), while Vietnam Journal of Earth Sciences, 40(3), 193-206 199 for the latter, the earthquake data used is not representative for the territory of Vietnam (Tran and Kiyomiya, 2012). There- fore, these two attenuation equations are still in the process of verification untill now. 4.3. Development of a desktop GIS tool: F-Hazard The first application of the Vietnam’s fault source model is called “F-Hazard” with a function of seismic hazard assessment from a scenario earthquake assumed to be originated by a tectonic fault. The software was designed in the desktop GIS environment, playing role of a DSS that allows automatic implementa- tion of various stages in a seismic hazard as- sessment procedure, such as selection of study region and active fault, definition of a scenar- io earthquake, and hazard calculation and mapping of seismic shaking distribution. Figure 4 illustrates the calculation proce- dure of the F-Hazard tool. As it can be seen from the figure, this is a five steps procedure, resulting in the ground shaking maps for the study area. The procedure starts with defini- tion of a study area. Then follows the selec- tion of a fault from GIS database, which is ca- pable of generating an earthquake in the se- lected area. The fault parameters are used to describe a source of the scenario earthquake assumed to be originated on the chosen fault. Then, a proper attenuation equation is chosen for computation of seismic hazard of the study area, according to the given scenario. Two ground motion parameters are used to express seismic hazard. The first parameter is Peak Ground Acceleration (PGA), in units of g, and the other one is shaking intensity I, character- izing the strength of shaking on the earth’s surface, reported on non-instrumental MSK- 64 scale. In results, a shake map of the study area in terms of PGA and I values is automat- ically displayed. The relationship between the values of PGA and intensity I is given in Table 2. The conversion is not implemented in the cases, when I is less than level V and I ex- ceeds level X, for there is no practical mean- ing in engineering seismology. Figure 4. A procedure for scenario-based seismic hazard assessment using the Vietnam’s fault-source model 5. Calculation and maping of seismic hazard 2. Select a fault-source 1. Define a study region 4. Define attenuation equation 3. Define a scenario earthquake Nguyen Hong Phuong, et al./Vietnam Journal of Earth Sciences 40 (2018) 200 Table 2. Relationship between values PGA and shaking intensity I (MSK-64 scale) PGA (g) Intensity I 0.015-0.03 V 0.03-0.06 VI 0.06-0.12 VII 0.12-0.24 VIII 0.24-0.49 IX > 0.49 X F-Hazard has been verified and validated through many research studies on seismic hazard assessment in Vietnam. Nevertheless, the desktop GIS environment makes the scope of application of F-Hazard is more or less lim- ited comparing with an internet environment. Besides, F-Hazard was designed with more intention focusing on a seismic hazard as- sessment tool, but not as an earthquake early warning tool. All above mentioned disad- vantages were taken into account in the de- velopment of a Web GIS based on-line DSS. 4.4. Development of a Web-GIS tool: RARE Based on the F-Hazard algorithm, an online tool for rapid assessment of seismic hazard from real-time earthquakes (RARE) was de- veloped and integrated into the DSS, using the Web GIS technology. In this case, the Vietnam’s fault source model was migrated in the DSS in terms of a map layer showing dis- tribution of all seismically active faults systems in the territory of Vietnam and adjacent sea ar- ea (Figure 5). With this layer activated, the user can query all attribute information of each fault source as well as to manipulate the tool. Figure 5. Map of seismically active faults systems in the territory of Vietnam and adjacent sea area in the DSS for on-line earthquake warning Vietnam Journal of Earth Sciences, 40(3), 193-206 201 Results of analyzing the GMPEs most suit- able for the Vietnam’s conditions lead to the following selection of attenuation models to be used in RARE: (i) The Campbell and Bozorgnia (1994) at- tenuation model. (ii) The Toro, Abrahamson and Shneider (1997) attenuation model. (iii) The Campbell-Bozorgnia (2008) at- tenuation model. (iv) The Bore-Atkinson (2008) attenuation model. (v) The Chiu-Young (2008) attenuation model. All of these attenuation models are devel- oped for shallow crust earthquakes and most suitable for the events with moment magni- tudes ranging from M5.0 to M8.0. The models 3, 4 and 5 were developed recently within the Next Generation Attenuation of Ground Mo- tion (NGA08) project lead by the Pacific Earthquake Engineering Research Center (PEER, 2008). The advantage of these models is that they have been developed using the most complete up to now database of strong- motion records of all over the world. It should be noted that although the source parameters are assigned automatically from the existing active faults database, the user can always change these values by more suit- able ones. For each attenuation model, the in- put parameters are changeable. To compute ground shaking, the user can select any period in a range from T = 0.01s to T = 10s. 5. Application of RARE for early earth- quake warning in Vietnam As RARE has the same function of a sce- nario-based seismic hazard assessment tool as its prototype, this paper will give an example of using the RARE in an earthquake warning procedure. For illustration, the event recorded on February 26th, 2017 in Nam Tra My, Quang Nam province is chosen as a scenario earthquake, with the following parameters de- termined: (i) Epicenter’s coordinates Longitude = 108.052 E; Latitude = 15.241 N; (ii) Magnitude: Mw= 3,9; (iii) Focal depth: H = 10 km. In order to use the RARE, the user needs to access to the “Earthquake Hazard” tab. Here, the whole procedure of scenario earthquake creation, calculation and display the shake map caused by the scenario earthquake is im- plemented by following the steps described below. (i) Input the parameters of the scenario earthquake. The “Choose earthquake scenar- io” window will allow user to input the pa- rameters of the scenario earthquake. There are two options for the user to input the parame- ters. The first option is to input manually the parameters into the “Longitude” and “Lati- tude” textboxes of the window. For the second option, from the Earthquake catalog shown in Figure 2, by clicking on “scenario” of the choosen earthquake in the last column on the right, the coordinates of the epicenter of sce- nario earthquake will automatically appear in the “Choose earthquake scenario” window (Figure 6). (ii) Selection of seismic source. In the “Fault source” drop-down list of the “Choose earthquake scenario” window, user should opt to choose one of the following types of seis- mic source: A point source can be selected when epi- center of the scenario earthquake does not match any fault in the active faults map. In this case, with assumption that earthquake is originated by a tectonic fault, an application called “Building a fault” will be provided to help user define a fault line crossing the epi- center of scenario earthquake, with the source parameters defined by user. Usually parame- ters of the fault located nearest to the epicen- ter in the map will be assigned for the newly built fault source. Rupture orientation is measured in degrees (0 to 360) clockwise from North. Rupture length is based on the default magnitude versus rupture length rela- tionship (Wells and Coppersmith, 1994) un- less the user chooses to override it. Vietnam Journal of Earth Sciences, 40(3), 193-206 202 Figure 6. Defining parameters of a scenario earthquake by RARE tool A fault source can be selected when epicen- ter of the scenario earthquake coincides with a fault source in the active faults map. In this case, the user needs to activate the layer of ac- tive faults by click on the “Fault source” check box on the left side of the map. Then the user can select a fault to define the source for the scenario earthquake simply by clicking on that fault. Usually a fault located nearest to the epi- center of scenario earthquake is chosen to be the source. Once selected, the fault source’s color will be changed to distinguish with the rest in the map. The user can also select a fault source from a drop-down list (Figure 7). For the chosen Nam Tra My scenario, the source selected is Hung Nhuong - Ta Vi fault, of which the geometric and geodynamic pa- rameters were automatically retrieved from the database of active faults systems (Dinh Van Toan et al., 2017). (iii) Selection of the attenuation models. The “Ground Motion Prediction Equation” drop-down list in the “Choose earthquake scenario” window allows the user to select a suitable attenuation model for the study region (Figure 8). A window will appear to allow updating suitable parameters for the chosen model. Figure 7. Selection of a fault source in RARE Vietnam Journal of Earth Sciences, 40(3), 193-206 203 Figure 8. Selection of an attenuation model in RARE (iv) Calculation and display the shake map caused by the scenario earthquake. After go- ing through all above-described steps, the user can click on the “Calculation” button to finish the procedure of hazard scenario definition. The RARE automatically calculates and dis- plays a shake map caused by the scenario earthquake for the study region. Figure 9 shows a shake map calculated for the chosen Nam Tra My earthquake. The col- or scale in lower part of the map is applied for both PGA (in g) and Intensity (MSK-64) val- ues. The RARE’s spatial analysis tools allow user to querry the ground shaking at any point on the map just by a click. The query infor- mation includes the point’s coordinates and the corresponding values of PGA and I (MSK-64) at that point. Figure 9. A shake map compiled from the real-time Nam Tra My earthquake using the RARE tool Beside the function of compiling shake map from a real-time earthquake, some other functions are integrated in the RARE that support the earthquake warning procedure in- cluding: - Create a report on the newly occurred earthquake; - Send emails to people and organiza- tions of different responsibility and regis- tered clients. Another application that can be developed within the DSS to support the earthquake warning process is the estimation of the num- ber of people, likely be affected by an earth- quake within 0.5ο (60 km) from the epicentre. As there is no reliable census data available for Vietnam at the moment, the test calcula- tion has been carried out using the shaking maps created by RARE and version 4 of the Nguyen Hong Phuong, et al./Vietnam Journal of Earth Sciences 40 (2018) 204 map of gridded population of the Word (GPW) issued by The A Data Center of NASA (Center for International Earth Science Information Network - CIESIN - Columbia University, 2016). The final product of the DSS is an earth- quake bulletin with the information on earth- quake parameters and its possible impacts in the area, affected by the earthquake. A part of the bulletin is illustrated on Figure 10. Figure 10. A part of an earthquake bulletin created by the DSS, showing the exposure population and the areas im- pacted by the earthquake 6. Discussions While having all properties of a tool for scenario-based seismic hazard assessment, the RARE appear to be much more advantageous comparing with F-Hazard thanks to a number of advances. On the one hand, application of Web GIS technology allows the use of RARE on any computer with internet connection and therefore considerably expands its scope of application. In addition, the most of attenua- tion models used in RARE were updated by recent ground motion prediction equations (GMPEs). On the other hand, in the RARE’s algorithm, the input parameters of each earth- quake scenario are taken directly from a real- time event, just occurred and recorded by the seismic network and therefore the results cal- culated by the RARE can be used for early warning purpose. The RARE produces grids of acceleration and intensity amplitudes in re- al-time display for specific users. The distri- Vietnam Journal of Earth Sciences, 40(3), 193-206 205 bution of shaking in an earthquake, whether is expressed as peak ground acceleration or in- tensity, provides responding organizations a significant increment of information beyond such parameters as magnitude and epicenter. Real-time ground shaking maps provide an immediate opportunity to assess the scope of an event to determine what areas were subject to the highest risk and probable impacts as well as those that received only weak motions and are likely to be undamaged. These maps will certainly find utility in supporting deci- sion making regarding mobilization of re- sources, damage assessment and aid to victims. To some extent, the shaking maps pro- duced by the RARE are comparable with those published on-line by USGS and some other international organizations (Wald, et al., 2003, 2006, Marreiros and Carrilho, 2012, Cauzzi et al., 2014). However, RARE should be regarded as a work in progress. At the moment, the system is still unable to generate the shaking maps derived from instrumental data due to the sparse distribution of the na- tional seismic network of Vietnam. In addi- tion, the automated mechanism to pick input parameters from on-line earthquake database for RARE to produce shaking maps will be the next task in the future. 7. Conclusions This paper describes the development of a DSS for earthquake warning service in Vietnam using Web GIS technology. The sys- tem consists of two main components: (1) an on-line database of earthquakes recorded from the national seismic network of Vietnam, and (2) a set of tools for rapid seismic hazard as- sessment. Using an on-line earthquake data- base, the system allows creating a shake map caused by a newly recorded earthquake. The results of the DSS will automatically be in- cluded in the earthquake bulletins issued na- tional wide by the Earthquake Information and Tsunami Warning Center, Institute of Ge- ophysics. The DSS developed is the means which help to disseminate the flow of earthquake in- formation to the public in fastest and most ef- ficient way. The DSS has proven to be a use- ful, descriptive display for rapidly assessing the scope and extent of shaking and potential damage following an earthquake. Maps are made available within several minutes after earthquake occurrence for public and scien- tific consumption via World Wide Web. The capability of the DSS in fast compu- ting/displaying results and issuing earthquake bulletins in the Internet environment allow not only considerably reduce the data processing time, but widely and quickly disseminate in- formation about an earthquake and its impact to the communities in the affected area. Also, the DSS can be used to produce Scenario Earthquake shaking maps, which provide the basis for pre-earthquake planning and under- standing the potential effects of large earth- quakes in the future. Moreover, the advantages of the Web GIS technology over desktop GIS in developing a tool for the RARE not only considerably ex- pand the scope of application of the tool itself, but also lead to a higher level of efficiency in seismic hazard assessment in Vietnam in fu- ture. The application of the on-line DSS in earthquake warning service can mitigate the earthquake risk as well as reduce the losses and damages due to earthquakes in Vietnam. Acknowledgements This research has been supported by a grant for the basic research project (No.105.05-2017.10) from National Founda- tion for Science and Technology Develop- ment (Nafosted) of Vietnam to Nguyen Hong Phuong. References Boore D.M., Joyner W.B. and Fumal T.E., 1994. Esti- mation of Response Spectra and Peak Acceleration from Wester North American earthquakes: an inter- im report, USGS open file report, 94-127, Menlo Park, California, United States Geological Survey. Nguyen Hong Phuong, et al./Vietnam Journal of Earth Sciences 40 (2018) 206 Boore D.M. and Atkinson G.M., 2008. Ground-Motion Prediction Equations for the Average Horizontal Component of PGA, PGV, and 5%-Damped PSA at Spectral Periods between 0.01 s and 10.0 s. Earth- quake Spectra, 24(1), 1-341. Bui Van Duan, Nguyen Anh Duong, 2017. The relation between fault movement potential and seismic activ- ity of major faults in Northwestern Vietnam. Vietnam J. Earth Sci., 39, 240-255. Campbell K.W. and Bozorgnia Y., 1994. Near-Source Attenuation of Peak Horizontal Acceleration from Worldwide Accelerograms Recorded from 1957 to 1993, Proceedings, Fifth U.S. National Conference on Earthquake Engineering, Chicago, Illinois, July 10-14: V(III), 283-292. Campbell K.W. and Bozorgnia Y., 2008. NGA Ground Motion Model for the Geometric Mean Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra for Periods Ranging from 0.01 to 10s. Earthquake Spectra, 24(1), 1-341. Cauzzi C., Edwards B., Fäh D., Clinton J., Wiemer S., Kastli F., Cua G. and Giardini D., 2014. On the cus- tomisation of shakemap for optimised use in Swit- zerland, 2014. Proceedings of the 2nd European Conference on Earthquake Engineering and Seis- mology, Istanbul, August 25-29, 1-10. Center for International Earth Science Information Net- work - CIESIN - Columbia University, 2016. Doc- umentation for the Gridded Population of the World, Version 4 (GPWv4). Palisades NY: NASA Socioec- onomic Data and Applications Center (SEDAC). Accessed April 2018. Chiou B.S.-J. and Youngs R.R., 2008. An NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra. Earthquake Spectra, 24(1), 1-341. Cornell, C.A., 1968. Engineering seismic risk analysis. Bull. Seis. Soc. Amer., 58(5), 1583-1606. Der Kiureghian and A. S-H. Ang, 1977. A fault rupture model for seismic risk analysis, Bull. Seim. Soc. Am., 67(4), 233-241. Douglas B.M. and Ryall A., 1977. Seismic risk in linear source regions, with application to the San Adreas fault, Bull. Seis. Soc. Amer., 67, 729-754. Marreiros, C. and Carrilho, F., 2012. The ShakeMap at the Instituto de Meteorologia. The proceedings of the 15th World Conference on Earthquake Engineer- ing, Lisbon, Portugal September 24-28. Nguyen Le Minh, et al., 2012. The first peak ground mo- tion attenuation relationships for North of Vietnam. Journal of Asian Earth Sciences. Doi: 10.1016/j.jseaes.2011.09.012. Nguyen Dinh Xuyen and Tran Thi My Thanh, 1999. To find a formula for computing ground acceleration in strong earthquake in Vietnam, J. Sci. of the Earth, 21, 207-213 (in Vietnamese). Pacific Earthquake Engineering Research Center, 2008. NGA model for average horizontal component of peak ground motion and response spectra. Earth- quake Spectra, 24(1), 1-341. Tran V.H. and Kiyomiya O., 2012. Ground motion at- tenuation relationship for shallow strike-slip earth- quakes in northern Vietnam based on strong motion records from Japan, Vietnam and adjacent regions, Structural Eng./Earthquake Eng., JSCE, 29, 23-39. Toro G.R., Abrahamson N.A. and Schneider J.F., 1997. Engineering Model of Strong Ground Motions from Earthquakes in the Central and Eastern United States, Seismological Research Letters, Janu- ary/February. Wald D.J., Worden B.C., Quitoriano V. and Pankow K.L., 2006. ShakeMap Manual. Technical manual, users guide, and software guide. Wald D.L., Wald B. Worden and Goltz J., 2003. ShakeMap - a tool for earthquake response. U.S. Geological Survey Fact Sheet 087-03. Wells D.L. and Coppersmith K.J., 1994. New Empirical Relationships Among Magnitude, Rupture Length, Rupture Width, and Surface Displacement, Bulletin of the Seismological Society of America, 84, 974-1002.