Application of artificial intelligence in earthquake forecasting

Transcription

1 Alcaton of artfcal ntellgence n earthquae forecastng Zhou Shengu, Wang Chengmn and Ma L Center for Analyss and Predcton of CSB, 63 Fuxng Road, Bejng P.R.Chna (e-mal zhou@ca.ac.cn; hone: ; fax: ). Sgnfcance It s stll very dffcult to forecast an earthquae u to now. However after a large earthquae, sesmologsts can often summarze a lot of henomena called earthquae recursors. Usng earthquae recursors and the occurrence regularty, some earthquae redctons have been made successfully by the sesmologcal exerts. But the earthquae recursors are very comlcated, and they do not reoccur smly. And there are a large number of varous henomena before the earthquaes. What s the relaton between those henomena and the earthquaes? Do the combnatons of those henomena reflect the earthquaes? Ths s a very comlcated roblem. Therefore, the comuter and artfcal ntellgence are used to study t. The varous recursory henomena are stored effectvely, the method of automatcally learnng s used to fnd out the relaton between earthquaes and varous henomena, and the comrehensve redcton s curred out by automatcally reasonng. It s undoubtedly very sgnfcant wor. As we now, Chna s an earthquae-rone country. The Chnese government has been ayng great attenton to the earthquae redcton. In order to reduce the loss caused by the earthquae dsaster, the earthquae consultaton meetngs are held for every wee, month and year by the organzatons of the varous regons n Chna. At resent, the earthquae redcton s stll based on varous recursors and sesmologst s exerences. If the daly wors (data rocessng, anomaly dscrmnaton and the comrehensve decson of earthquae redcton) are done by comuter automatcally. It s not only for the earthquae redcton exerts to save ther tme, but also t maes the earthquae redcton more objectve, overall, and easy to summarze and mrove. The structure of the IDSSEP We develoed an Intellgent Decson Suort System for Earthquae Predcton (ID- SSEP) to hel sesmologsts to forecast earthquaes. The general structure and flowchart of IDSSEP s shown n fgure. It conssts of several databases and rocessng subsystems. 477

2 Knowledge reresentaton Accordng to the features of exerences of the earthquae redcton exerts and the earthquae cases, we adot the followng format to reresent the nowledge of earthquae forecastng: IF A E T T 2 A 2 E 2 T 2 T 22 B/P A K E K T K T K2 B/P THEN AT T 2 C MtM M 2 Mm P Every rule s comosed of several remses (condton) and one concluson, and the remses must meet certan relatonsh n tme order. There are 5 attrbutes n a remse, whch are defned as follows: A I... Area or staton where anomaly aears. E I... A certan recursory anomaly T... Delay erod. Ths anomaly must aear delayng T after the recedng anomaly or the frst anomaly aears. T 2... Effectve erod. After ths anomaly ends t s stll ossble that earthquaes occur durng T 2 erod. P/F... P reresents that ths anomaly must delay after the recedng anomaly, F reresents that ths anomaly must delay after the frst anomaly. The concluson contans the followng 9 attrbutes: A... Area of comng earthquae T... Parameter for calculatng orgn tme. T 2... Parameter 2 for calculatng orgn tme. C... Parameter 3 for calculatng orgn tme. Mt... Method for calculatng orgn tme. For nstance, when Mt=4, the C reresents the order number of the remse, T reresents the onset tme of the anomaly related to the remse, T 2 reresents the end tme of ths anomaly. Durng the T T 2 erod, the earthquae wll occur. M... Parameter for calculatng magntude M 2... Parameter 2 for calculatng magntude Mm... Method for calculatng magntude. For nstance, When Mm= M s the mnmum magntude of the comng earthquae, M 2 s the maxmum magntude of the comng earthquae. P... Probablty of Earthquae Occurrence(PEO). A may be defned as any area or any staton n a rule. It means ths rule can ft anywhere. It s very easy to store and manulate the nowledge reresented n such format. Reasonng method The exerences of earthquae redcton exerts are gathered, sorted out, formalzed, and then are stored n nowledge database as rules. Generally there are tens or hundreds of rules n the nowledge database. Meanwhle, varous anomales aearng as events are 478

3 sorted out and stored n the event database n unform format. An event record ncludes the followng attrbutes: A... Area or staton where the anomaly aears E... A certan recursory anomaly t... Onset tme of the anomaly t 2... End tme of the anomaly. If the anomaly hasn't ended, t s defned as resent tme. V... Characterstc value of the anomaly. CF... Certanty factor of the anomaly. Parameters Observed Data for Precursors Earthquae Catalogue Anomaly Obtanng Subsystem Learnng Subsystem Events Knowledge Database management Subsystem Reasonng subsystem (All Databases) Predcton Onons Fgure. Comonents and flowchart of IDSSEP Reasonng s a rocess that matches remses of a rule wth events. If all remses n a rule are matched fully, then the concluson of the rule s tenable. Because the value of observatons are varyng contnuously, robably several anomales of an observaton aear durng a erod. Therefor, t s ossble that there s more than one combnaton of anomales related to remses of one rule. Every combnaton must be judged to see f t fts the relatonsh n tme order. Maybe several combnatons are matched. As mentoned above, the A of remses may be any area. In ths case, f an area contans all anomales concerned n remses of a rule and they are ftted n tme order, then the regon of a comng earthquae s calculated accordng to the areas of anomales and arameters. 479

4 Thus t can be seen that one rule can be matched several tmes successfully, namely t s ossble to redct several earthquaes n dfferent regons and dfferent erods usng one rule. More conclusons wll be obtaned when varous rules are used. Assgn N redctve conclusons are obtaned: A Predcted area of the th concluson T T 2 Predcted erod of the th concluson M M 2 Predcted magntude of the th concluson P Predcted robablty of the comng earthquae. It s gotten from P of related rule and CFs of related anomales by comutng. Generally, these redcted results are n dfferent areas, dfferent erods and dfferent magntudes, and they are overlaed together. Every redctve result s an amount wth four dmensons and one occurrence robablty. For gettng the comrehensve redctve concluson from those ndvdual results, we synthesze them n sace, tme and magntude searately. Frst get the satal robablty dstrbuton ma. Then on the ma dstngush some regons where the robablty value s relatvely larger than others. Fnally let every regon dstngushed as the target regon, reason several tmes agan and agan to get more exact robabltes and ther satal, tme, magntude dstrbuton mas. To calculate the satal dstrbuton of PEO, We dvde a regon nto squares formed by lattude lnes and longtude lnes, and code these squares from bottom to to and from left to rght. Assgn one square (jth) s redcted by m conclusons, and P (=,2...m) are the PEO of the th concluson, then the PEO of the square redcted by the th concluson s: P / NN r, () ( l ),, l< where r.l s the correlaton coeffcent between the th rule and the lth rule, and NN K s the total number of squares of the regon redcted usng the concluson. The synthetc PEO of the square (jth) s calculated by followng recurson formula: P = j m = = +, (=2 m) For any desgnated regon A, ts PEO s calculated by the followng recurson formula: P = P P A = P = n mm P P = where mm s the number of common squares of the regon A and the regon redcted by the th concluson. Usng the smlar way, we can calculate the tme PEO and ts dstrbuton, as well as magntude PEO and ts dstrbuton. Fnally, for a gven regon, erod and magntude range, ther PEO s the mnmum one of the regon PEO, tme PEO and magntude PEO., (=2 n) 480

5 Alcaton The IDSSEP was mlemented n 995, and rovded the analyss onon for the annual earthquae trend consultaton for all areas of Chna. The results redcted n 995 and 996 were very successful and well receved by the Chna Sesmologcal Bureau. In 997, 9 rs regons were rased usng the system. Among whch, Jash earthquae wth M6.6 n Xnjang, Kunlunshan earthquae wth M5.4 n Qngha, Chongqng earthquae wth M5.2, Ljang-Jangcheng earthquae wth M5.5 n Yunnan, Lancheng earthquae wth M5.2 n Fujan, one after another occurred. However, there was not strong earthquae n the two rs regons of North Chna (border of Hebe and Inner Mongola, northwestern Bejng, and Boha Sea) by the end of 997. In December of 997, the research grou analyzed the earthquae stuaton of 998 usng IDSSEP, and found that there was stll abnormal henomenon on the border of Hebe and Inner Mongola, northwestern Bejng. Therefore, t was stressed agan that there would be stll occurrence ossblty of strong earthquae n the regon. In Jan.0, 998, the Zhangbe earthquae wth M6.2 n Zhangjaou regon occurred n the center of the redcted area. On the bass of some analyses, t was consdered that there would be ossblty for a strong earthquae occurrng after the Zhangjaou earthquae. But, the research grou onted out that there would not be larger earthquae n Zhangjaou and ts vcnty, esecally n Bejng area, by use of IDSSEP. The result has shown that the redcton onon for the Zhangjaou earthquae and the onon wthout earthquae n Bejng area are concordant wth the real facts. Reference [] Zhou Shengu, Wang Chengmn et al: The Archtecture of Intellgent Decson Suort System, 2 nd Symosum of Intellgent Interface and Intellgent Alcaton of Chna, 685~690, 995. [2] Zhou Shengu et al: Knowledge Reresentaton and Calculaton of Earthquae Occurrence Probablty, Thrd symosum of Intellgent Interface and Intellgent Alcaton of Chna, 574~578, 997. [3] Zhou Shengu, Shen Yu et al: Overvew on the Practcal System for Earthquae Predcton, Earthquae Research n Chna, Vol.9 No. 33~38, 993. [4] Zhang Zhaocheng et al: Earthquae Cases of Chna, Vol. -3, Earthquae Press, 989. [5] Adams J B.: A Probablty Model of Medcal Reasonng and the MYCIN Model. Mathematcal Boscence, Vol.32, 77~86, 976. [6] Wu Qanyan et al: Artfcal Intellgence and Exert System, Defense Scence & Technology Unversty Press, 997. [7] Zhuang uengyan et al: Exert System for Earthquae Forecastng, Earthquae Press,