Tectonic Setting Indonesia dan Pemodelan gempa dan Tsunami

Transkripsi

1 Pelatihan Pemodelan Tsunami Run-up, RISTEK, 20 Agustus, 2007 Tectonic Setting Indonesia dan Pemodelan gempa dan Tsunami Danny Hilman Natawidjaja Geoteknologi LIPI

2 Indonesia kaya SDA dan bencana Gempabumi Tsunami Letusan gunung api Longsor Banjir Angin topan Badai Kebakaran hutan alam, dll.

3 Danny H. Natawidjaja RUTI 2005

4 Mitigating Earthquake and Tsunami SOURCE What? Where? How big? When? Banyak disepelekan! PHYSICAL MODELING HAZARDS Surface faulting Shaking Tsunami Landslides liquefaction

5 Model Tsunami (Run-up) yang baik Input data sumber gempa/tsunami yang dapat dipertanggung jawabkan Pemilihan scenario parameter sumber yang masuk akal secara ilmiah Data bathimetri dan topografi serta tutupan lahan yang se-akurat mungkin Mengerti keterbatasan pemodelan tsunami, baik karena simplifikasi matematis dari proses alam juga karena asumsi-asumsi yang dipakai yang disebabkan ketidaktahuan data sumber yang sebenarnya

6 DATA CONSTRAINTS ON TSUNAMI MODEL PARAMETER DASAR: Bathimetri topografi (utk run-up modeling) PARAMETER UTAMA SUMBER geometri sumber: panjang-lebar, lokasi arah dan besar pergerakan pengangkatan dan penurunan muka bumi arah rupture dan cepatnya pergerakan mm/year PARAMETER SEKUNDER: Cabang patahan di dekat palung longsoran di bawah laut

7 Eurasian Plate Pacific Plate 12 cm/yr 5-6 cm/yr India-Australian Plate Indonesia is an earthquake country : Crustal motions from GPS (Bock et al, 2004)

8 Earthquake in Indonesia since 1964

9 trench Forearc islands Moho Megathrust earthquake ZONA SUBDUKSI

10 Interseismic period (slow strain accumulation) It is like a spring board! Slow uplift Slow Submergence

11 Co-seismic = earthquake (sudden strain release) It is like a spring board! Sudden Uplift

12 Co-seismic = earthquake (sudden strain release) Initial Tsunami Formation

13 Locking zone (=seismic zone= zone of strain accum.) Depth<60km

14 Tsunami modeling Wave-propagation: F(depth) Shoreline interaction Bathi & topo detil SOURCE Fault parameters

15 Epicenter data of Aceh earthquake day after

16 Max. slip 20m M 8.9 Preliminerary Rupture Source Model of Dec 2004 Aceh Earthquake Chen JI - Caltech

17 The early model of Aceh Tsunami 2004 (Steve Ward)

18 ANIMATION of The 2004 Aceh tsunami (Hamzah Latief) Ward ChenJi Vertical displacement of seafloor estimated by Hirata et al. [2005] from satellite altimetry data. Tsunami source base on the Altimetry Data (Tsunami Research Group Marine Research Center ITB)

19 We have used METHODS OF STUDYING THE SOURCE records of sea-level change in corals and satellite imagery GPS To understand the behavior of the tsunami source

20 Model G M w 9.2 Rupture: ~1600km long meter Displacement westward Based on: Coral Satelite imagery analysis GPS campaign mode Continuous GPS (far field) (after Chlieh et al, 2005 and Subarya et al, Nature, March 2006)

21 Source parameters Uplift in 2004 Of Aceh Tsunami 2004 The greatest uplift occurred west of the Nicobar islands and southwest of Aceh Courtesy of Mohamed Chlieh

22 Mengenal sumber gempa-tsunami Indonesia

23 Gempa Sumatra (yg paling banyak dipelajari)

24 trench Forearc islands Sumatran Fault Zone Moho Megathrust earthquake Sumatran earthquake (the most well understood)

25 1941 (7.9) 1935 (M7.7) 1881 (7.9) (~M7.8) 1861 (M~8.5) 1797 (M8.4) 1833 (8.9) Plate movement 2004 (M9.15) mm/year Sumatran fault Zone 2000 (M7.8) INDIAN-AUSTRALIAN PLATE EURASIAN PLATE Malaysia 2005 (M 8.7) Currently locked, Near end of cycle section Jakarta Un known section, No large eartquakes in Historical records

26 Briggs et al., Science, 2006

27 the 2004 earthquake

28 the 2005 earthquake

29 Paleoseismic history Simeulue island uplift tsunami uplift SIMELUE ISLAND uplift uplift Similar to dates of uplifted coral and subsided mangrove in the Andaman islands (Rajendran et al 2007) Similar to dates of uplifted coral terrace in the Andaman islands and possible tsunami deposit on east coast of India (Rajendran et al 2007)

30 Paleoseismic history Simeulue island SE Simelue: uplift tsunami uplift NW Simelue: uplift 1400 SIMELUE ISLAND uplift 965 NW: 400 to 600 year recurrence? SE: 140 to 200 year recurrence?

31 Drawn beach north of Calang, Aceh area, July 2007

32 Paleotsunami study in Banda Aceh area, July 2007

33 A tear in the over-riding plate? Batee fault

34 Batee fault March 28,2005 Slip on the megathrust

35 Model sumber gempa di zona subduksi Rupture/sumber gempa

36 A A hingeline uplift subsidence Rupture zone

37 A A hingeline uplift subsidence Rupture zone

38 May 2005 January 2005 Near Afulu village, west coast of Nias island

39 The March 2005 event resulted in impressive uplift Old high tide Old low tide Examples from Nias, Simeulue and the Banyak islands Old high tide New high tide

40 dan wilayah di timurnya turun Haloban village, Banyak islands

41 But, how about big tsunami in 1861 Nias earthquake? A Historical sketch of the 1861 earthquake in Nias

42 Batee fault March 28,2005 Slip on the megathrust 1861?

43 Dimana Selanjutnya? Segmen Mentawai!!!

44 Stress Shadow dan Efek pemicuan gempabumi (Mc Closkey)

45 Coastlines show subsidence of the Mentawais for many decades

46 In Mentawai Island Evidence for giant earthquakes in 1797 and 1833 Fossil microatolls in the intertidal zone, east coast of North Pagai island

47 ~1370 ~ & 1833 Paleogeodetic For ~700 years Elevation relative to modern sea level (cm) The Mentawai patch appears to be timepredictable and near failure Years (AD)

48 SEISMIC GAP: Before Aceh- Andaman Earthquake Malaysia Sumatra

49 SEISMIC GAP: Malaysia After Aceh Andaman Earthquake Before Nias Earthquake Sumatra

50 SEISMIC GAP: Malaysia After Nias Earthquake Is Mentawai Seismic gap Sumatra How about Jawa??

51 SuGAr Velocity Field Up to June 2006 Ongoing Post-slip Ongoing Squeezing Of Mentawai

52 This locked patch broke in 2005 These locked patches are the likely source of the next great Mentawai earthquake and tsunami Chlieh et al (in review) J Geophys Res

53 Padang in 1797 (~4,000 people) Padang now (~800,000 people) Photo: Jose Borrero

54 Earthquake and Tsunami Scenarios for Western part of Sumatra Patterns of Uplift of the seafloor produced by the six megathrust ruptures scenarios (Borero et al, 2006) Scenario 1 Scenario 2 Scenario 3 Scenario 4 D.H. Natawidjaja May 2007

55 Animasi proses deformasi gempa dan tsunami

56 Animasi proses deformasi gempa dan tsunami

57 Animasi proses deformasi gempa dan tsunami Tidak Surut dulu Surut dulu Surut dulu

58 Tsunami simulation for an Aceh-2004-like source Scenario 3: Uplift from 20 m slip on 700-km megathrust rupture (Borero et al, 2006)

59 20-m Slip Scenario in Padang D.H. Natawidjaja May 2007

60 10-m Slip Scenario in Padang

61 20-m Slip Scenario in Bengkulu D.H. Natawidjaja May 2007

62 10-m scenario

63 20-m scenario

64 20-m scenario Turun 0.5 meter

65 10-m scenario

66 20-m scenario

67 20-m scenario Turun 1.5 meter

68

69 Sumber Gempa - Tsunami Jawa (sedikit tahu, banyak tidaknya)

70 SUMARY OF JAVA EARTHQUAKE (modified from Newcomb and McCann, 1987) 2006 tsunami M7.8) 1994 (Pancer) M 7.8 Time Very old subducted oceanic crust (~150 million years old) Less-frequent earthquakes and no M 8 EQ in the history But what did not happen does not mean would not happen

71 It lead to a big question What is the maximum magnitude of earthquake of the Jawa Subduction zone? July 2006 (Mw 7.8) SEISMIC GAP Is it actually less than M8? How about in a much longer time?? 1994 (Mw 7.8) Seismic record for the past 30 years

72 Bagaimana memilih tsunami source Yang tepat untuk Selatan Jawa??? M 7.8

73 Bagaimana memilih tsunami source Yang tepat untuk Selatan Jawa??? M 7.8

74 Bagaimana memilih tsunami source Yang tepat untuk Selatan Jawa??? M 7.8

75 Bagaimana memilih tsunami source Yang tepat untuk Selatan Jawa??? M 9.0

76 Bagaimana memilih tsunami source Yang tepat untuk Selatan Jawa??? M 9.0

77 Gempa Jakarta 1699 D.H. Natawidjaja May 2007 Historical On-land Earthquakes of Jawa (Natawidjaja, 2006)

78 Gempa Jakarta!!! Hikayat Jakarta / Willard A. Hanna. Yayasan Obor Indonesia Ed. 1 ISBN Pada akhir abad ke-18, citra Ratu Timur itu menurun drastis. Willard A. Hanna (Hikayat Jakarta) mencatat, bahwa kejadian itu diawali oleh gempa bumi yang bukan main dahsyatnya, malam tanggal 4 dan 5 November 1699, yang menyebabkan kerusakan besar pada gedung-gedung dan mengacaukan persediaan air dan memporak-porandakan sistem pengaliran air di seluruh daerah. Gempa itu disertai letusanletusan gunung api dan hujan abu yang tebal, yang menyebabkan terusan-terusan menjadi penuh lumpur. Aliran sungai Ciliwung berubah dan membawa sekian banyak endapan ke tempat dimana sungai itu mengalir ke laut, sehingga kastil yang semula berbatasan dengan laut, seakan-akan mundur sedikit-dikitnya 1 kilometer ke arah pedalaman.

79 Gempa-Tsunami di Indonesia Timur (sumber-nya paling potensial tapi sangat kurang dipelajari)

80 Earthquake and Tsunami of East Indonesia Region Active Tectonics

81 Earthquake and Tsunami of East Indonesia Region Active Tectonics

82 Earthquake and Tsunami of East Indonesia Region Earthquakes M>5: (Engdahl, 2006) D.H. Natawidjaja May 2007 < 30 km depth km

83 Earthquake and Tsunami of East Indonesia Region Recent Earthquake Mw > 7 since 1973 D.H. Natawidjaja May 2007

84 Earthquake and Tsunami of East Indonesia Region D.H. Natawidjaja May 2007 Historical Earthquake since 1600 (USGS)

85 Earthquake and Tsunami of East Indonesia Region D.H. Natawidjaja May 2007 Tsunamigenic earthquake zones and Historical Tsunami

86 Earthquake and Tsunami of East Indonesia Region Tsunami database from H.Latief Historical Tsunami: Year (Run-up in m)

87 Earthquake and Tsunami of East Indonesia Region Historical Tsunami: Year (death) Tsunami database from H.Latief

88 Bagaimana dengan tsunami source untuk wilayah Maluku? M 8.0

89 Bagaimana dengan tsunami source untuk wilayah Maluku? M 8.0

90 Bagaimana dengan tsunami source untuk wilayah Maluku? M 8.0

91 Bagaimana dengan tsunami source untuk wilayah Maluku? M 9

92 Probability map of tsunami-height hazards in Southeast Asia Paul Sommervile & Hng Kie Thio (URS) Hanya memakai Data seismic dari tahun 1973?? Anda percaya??? Bagaimana kualitas data sumber Data from yang URS digunakan?

93 Concluding remarks RESEARCH Knowledge of Earthquake and Tsunami Sources, HAZARD-RISK MODELS Tsunami modeling Designing Observation Network and System for Research and Early Warning System Public Education and Community Preparedness Infrastructure changes, Evacuation plan, and Post-Disaster actions

94 Terima kasih Tunas kelapa yang tumbuh setelah gempa Maret 2005, P. Wunga, Nias, Juni 2006