Introduction to Engineering Seismology Lecture 18

Transcription

1 Lectue 18: Intoduction to GIS, Integation of hazad paametes on GIS platfom; Final zonation map pepaation with case study of Bangaloe Topics Geogaphical Infomation System (GIS) Analytic Hieachy Pocess (AHP) Eathquake hazad paametes Themes and its weights fo GIS integation Hazad Index Deteministic seismic micozonation map Pobabilistic seismic micozonation map Keywods: Hazad integations, Geogaphic Infomation System, Eathquake Hazad Paametes, Micozonation maps Topic 1 Geogaphical Infomation System (GIS) Geogaphic infomation systems (GIS) o geospatial infomation systems is a set of tools that captues, stoes, analyzes, manages, and pesents data that ae linked to location(s). In the simplest tems, GIS is the meging of catogaphy, statistical analysis, and database technology. GIS may be used in geogaphy, catogaphy, emote sensing, land suveying, public utility management, natual esouce management, pecision agicultue, photogammety, uban planning, emegency management, navigation, aeial video, and localized seach engines. GIS will povide an effective solution fo integating diffeent layes of infomation thus poviding a useful input fo city planning and in paticula input to eathquake esistant design of stuctues in an aea. Geogaphical Infomation System (GIS) povides a pefect envionment fo accomplishing compehensive egional seismic damage assessment, GIS has the capability to stoe, manipulate, analyze and display the lage amount of equied spatial and tabula data. One of the most impotant featues of GIS is the manipulation and analysis of both spatial (gaphic) and non-spatial (non-gaphic) data. The pocedues fo data analysis typically found in most GIS pogams ae as follows: D. P. Anbazhagan 1 of 11

2 1. Map ovelay pocedues, including aithmetic, weighted aveage, compaison, and coelation functions. 2. Spatial connectivity pocedues, including poximity functions, optimum oute selection and netwok analysis. 3. Spatial neighbohood statistics, such as slope, aspect atio, pofile and clusteing. Measuements of line and ac lengths, of point-to-point distances, of polygon peimetes, aeas and volumes. 4. Statistical analysis, including histogams o fequency counts, egessions, coelations and coss-tabulation. 5. Repot geneation, including maps, chats, gaphs, tables and othe usedefined infomation. Figue 18.1 below shows the typical nitation GIS flow chat. Depending on the level of sophistication of a GIS, numeous application-specific analysis functions may exist. These include pocedues such as geotechnical data, ai pollution dispesion, gound wate flow, a highway taffic outing. Automated Mapping System Spatial Modeling System Map Infomation System Fully Integated GIS System Analysis and Modeling System Data Base Management System Non-Spatial Modeling System Fig 18.1: The infomation systems composing a fully integated GIS (afte Fost et al., 1992) Most of the systems include some sot of built-in pogamming capability usually in the fom of a softwae-specific maco language. This allows the use to develop a set of functions o analysis pocedues that can be stoed in a use-defined libay. Often, the GIS maco language is vey simplified and doesn t have to handle vey high-level computational featues such as ecusion, numeous simulations, subscipted vaiables, and suboutines. Fo this eason, most GIS pogams have the ability to communicate with extenal analysis and modeling pogams. A system can typically output data in vaious fomats to be used in vaious extenal pogams such as speadsheets, wod pocessing, gaphics, and othe use-specified executable pogams. D. P. Anbazhagan 2 of 11

3 Topic 2 The esults of an extenal analysis can be used by GIS as both gaphic and nongaphic data fo futhe manipulation and analysis, o fo final epot and map geneation. ith these wide aeas of application, GIS play a unique ole fo hazad pepaedness and management. Analytic Hieachy Pocess (AHP) Saaty's Analytical Hieachy pocess constucts a matix of pai-wise compaisons (atios) between the factos of eathquake hazad paametes (EHP). The constucted matix shows the elative impotance of the EHP based on thei weights. If 9 eathquake hazad paametes ae scaled as 1 to 9, 1 meaning that the two factos ae equally impotant, and 9 indicating that one facto is moe impotant than the othe. Recipocals of 1 to 9 (i.e., 1/1 to 1/9) show that one is less impotant than othes. The allocation of weights fo the identical EHP depends on the elative impotance of factos and paticipatoy goup of decision makes. Then the individual nomalized weights of each EHP ae deived fom the matix developed by paiwise compaisons between the factos of EHP. This opeation is pefomed by calculating the pincipal Eigen vecto of the matix. The esults ae in the ange of 0 to 1 and thei sum adds up to '1' in each column. The weights fo each attibute can be calculated by aveaging the values in each ow of the matix. These weights will also sum to '1' and can be used in deiving the weighted sums of ating o scoes fo each egion of cells o polygon of the mapped layes. Since EHP vay significantly and depends on seveal factos, they need to be classified into vaious anges o types, which ae known as the featues of a laye. Hence each EHP featues ae ated o scoed within EHP and then this ate is nomalized to ensue that no laye exets an influence beyond its detemined weight. Theefoe, a aw ating fo each featue of EHP is allocated initially on a standad scale such as 1 to 10 and then nomalized using the elation, Ri Rmin Xi Rmax Rmin (18.1) hee, R i is the ating assigned fo featues with single EHP, R min and R max is minimum and maximum ate of paticula EHP. D. P. Anbazhagan 3 of 11

4 Topic 3 Eathquake hazad paametes Eathquake hazad analysis equies and assessment of eathquake hazad paametes and the futue of eathquake potential in a egion. Eathquake hazad paametes such as, 1. maximum egional magnitude M max 2. activity ate λ, and 3. the b paamete in the Gutenbeg-Richte distibution Maximum egional magnitude M max - The maximum magnitude is an impotant vaiable in the seismic hazad estimation as it eflects maximum potential of stain eleased in lage eathquakes. The instumental and histoical ecods of eathquakes ae often too shot to eflect the full potential of faults o thusts. The maximum egional magnitude, Mmax, is defined as the uppe limit of magnitude fo a given egion o it is magnitude of lagest possible eathquake. In othe wods it is a shap cut-off magnitude at a maximum magnitude Mmax, so that, by definition, no eathquakes ae to be expected with magnitude exceeding Mmax. Activity ate λ - The ate of seismicity vaies with time. Though afteshock sequences can stongly influence the ate, they ae not the only eason fo the vaiation. Defining a seismicity ate equies seveal things. Fist off, egion must be defined fo which one want to find a ate. That aea can be any size. Boundaies can be assigned even in depth, so that one is actually counting the ate of eathquakes within a paticula volume. hateve one chooses, the boundaies should be definite, and fixed. Natually, to count eathquakes, you need a way to ecod and locate eathquakes, o access to a eliable souce of data (aleady ecoded fo you). Thee ae many seismic databases aound the wold that offe infomation to the public. The b paamete in the Gutenbeg-Richte distibution - It has been obseved fom the ealie analysis that the data set is not complete fo the inteval 1807 to Geneally b value is computed fom the analysis of whole set of data without testing the completeness of the data which gives eo in the estimation of b value. D. P. Anbazhagan 4 of 11

5 Topic 4 Following the method poposed by Stepp (1972), it was found that data set is complete since Hence, computation of b value is caied out using the data set fom 1967 to Geomophological Attibutes - The geomophological attibutes ae the geology and geomophology (GG), ock depth/ soil thickness (RD/ST), soil type and stength (epesented in tems of aveage shea wave velocity) (SS), dainage patten (DP) and elevation level (EL). Seismological Attibutes - The seismological thematic maps have been geneated based on detailed studies of seismic hazad analysis, site esponse studies and liquefaction analysis. Fom these studies diffeent eathquake hazad paametes ae mapped. But fo final Index map pepaation and GIS integation only selected maps ae consideed as themes which ae: 1. PGA at ock level at 10 % pobability in 50 yeas exceedance based on PSHA. 2. Amplification facto based on gound esponse analysis using SHAKE Pedominant fequency based on site esponse and expeimental studies. 4. Facto of safety against Liquefaction potential. Themes and its weights fo GIS integation Table 18.1: Themes and its weights fo GIS integation Index Themes eights PGA Rock level PGA using DSHA-DPGA 9 Rock level PGA using PSHA-PPGA 9 AF Amplification facto 8 ST Soil Thickness using boehole 7 SS Equivalent Shea wave velocity fo 6 Soil FS Facto of safety against liquefaction 5 PF Pedominant peiod / fequency 4 EL Elevation levels 3 DR Dainage patten 2 GG Geology and geomophology 1 Table 18.1 gives weights of each theme used fo hazad index mapping D. P. Anbazhagan 5 of 11

6 In this method, a matix of pai-wise compaisons (atio) between the factos is built, which is used to deive the individual nomalized weights of each facto. The pai-wise compaison is pefomed by calculating the pincipal Eigen vecto of the matix and the elements of the matix ae in the ange of 0 to 1 summing to '1' in each column. The weights fo each theme can be calculated by aveaging the values in each ow of the matix. These weights will also sum to '1' and can be used in deiving the weighted sum of ating o scoes of each egion of cells o polygon of the mapped layes. Since the values within each thematic map/laye vay significantly, those ae classified into vaious anges o types known as the featues of a laye. Table 18.2 gives the pai-wise compaison matix of themes and the calculated of nomalized weights. ithin individual theme a gouping has been made accoding to thei values. Then ank is assigned based on the values. Usually these anks vaies fom 1 to 10, highest ank is assigned fo values moe hazad in natue. Table 18.2: Pai-wise compaison matix of Themes and thei nomalized weights Theme PGA AF ST Vs FS PF EL DR GG eights PGA 1 9/8 9/7 9/6 9/5 9/4 9/3 9/2 9/ AF 8/9 1 8/7 8/6 8/5 8/4 8/3 8/2 8/ ST 7/9 7/8 1 7/6 7/5 7/4 7/3 7/2 7/ Vs 6/9 6/8 6/7 1 6/5 6/4 63 6/2 6/ FS 5/9 5/8 5/7 5/6 1 5/4 5/3 5/2 5/ PF 4/9 4/8 4/7 4/6 4/5 1 4/3 4/2 4/ EL 3/9 3/8 3/7 3/6 3/5 3/4 1 3/2 3/ DR 2/9 2/8 2/7 2/6 2/5 2/4 2/3 1 2/ GG 1/9 1/8 1/7 1/6 1/5 1/4 1/3 1/ These anks ae nomalized in ange 0-1. The assigned anks with nomalized values ae given in Table D. P. Anbazhagan 6 of 11

7 Table 18.3: Nomalized anks of the themes Themes Values eight Ranks Nomalized Ranks SOT (m) > EVS(m/s) > FSL < >2 1 0 DPGA (g) > SRAF >4 4 1 SPF (Hz) PPGA (g) D. P. Anbazhagan 7 of 11

8 Topic 5 Hazad Index Topic 6 Based on above attibutes, two types of hazad index map ae geneated. 1. One is deteministic seismic micozonation map (DSM), which is basically deteministic hazad index map using PGA fom deteministic appoach and othe themes. 2. Anothe map is the pobabilistic seismic micozonation map (PSM). Pobabilistic hazad index ae calculated simila to DSM but PGA is obtained fom pobabilistic seismic hazad analysis. Hazad index is the integated facto, depends on weights and anks of the seismological and geomophological themes. Theme weight can be assigned based on thei contibution to the seismic hazad. Rank can be assigned with in theme based on thei values close to hazads. Usually highe ank will be assigned to values, which is moe hazadous in natue, fo example lage PGA will have the highe ank. The contibuting themes and thei weights ae listed below in the above Table. Once the identical weights ae assigned then nomalized weights can be calculated based on the pai-wise compaison matix. Some of the attibutes (like PGA and Vs) has two values fo the same theme, hence both ae given same weights with diffeent pecentage. The nomalized weights ae calculated using Saaty's Analytical Hieachy Pocess (Nath, 2004). Deteministic seismic micozonation map Deteministic seismic micozonation map is hazad index map fo wost scenaio eathquake. Impotant facto of PGA (weight is 9) is estimated fom synthetic gound motions, which ae geneated based on MCE of 5.1 in moment magnitude. Hazad index values ae estimated based on nomalized weights and anks though the integation of all themes using the following equation: DPGA DPGA AF AF STST SSSS DSM / (18.2) FS FS PF PF EL EL DR DR GG GG Using estimated values deteministic seismic micozonation map has been geneated. D. P. Anbazhagan 8 of 11 w w

9 Figue 18.2 shows the deteministic seismic micozonation map fo Bangaloe. Integated GIS map shows that hazad index values vay fom 0.10 to These values ae gouped into six goups, <0.1, , , , and 0.6 to The maximum hazad is attached to the seismic hazad index geate than 0.6 at westen pat of Bangaloe. Easten pat of city attached to a minimum hazad when compae to othe aeas. esten and southen pat has mixed hazad and nothen pat has modeate hazad. Topic 7 Pobabilistic seismic micozonation map Simila to DSM hazad index calculation, pobabilistic hazad index has been estimated, but PGA values ae taken fom the pobabilistic seismic hazad analysis. PGA at 10% pobability of exceedance in 50 yeas has been estimated consideing six seismogenic souces and egional ecuence elation. Based on pobabilistic hazad index values pobabilistic seismic micozonation map (PSM) has been geneated. Pobabilistic hazad index values ae estimated based on nomalized weights and anks though the integation of all themes using the following equation: PSM PPGA FS FS PPGA PF PF AF EL AF EL ST ST DR DR SS SS GG GG (18.3) Figue 18.3 below shows the pobabilistic seismic micozonation map based on calculated hazad index. Pobabilistic hazad index values vay fom 0.10 to 0.66 and has been gouped to six such as <0.1, , , , and 0.6 to D. P. Anbazhagan 9 of 11

10 Fig 18.2: Deteministic seismic micozonation map of Bangaloe D. P. Anbazhagan 10 of 11

11 Fig 18.3: Pobabilistic seismic micozonation map of Bangaloe These values ae lesse that deteministic hazad index. The maximum hazad is attached to the seismic hazad index geate than 0.6 at south westen pat of Bangaloe. Lowe pat (south) of Bangaloe is identified as modeate to maximum hazad when compaed to the nothen pat. End of Lectue 18 Intoduction to GIS, Integation of hazad paametes on GIS platfom; Final zonation map pepaation fo hazad and isk D. P. Anbazhagan 11 of 11