EARTHQUAKE HAZARD AND RISK ZONATIONS OF THE SUMATERA ACTIVE FAULT (SEGMENT SIANOK), BUKITTINGGI AND SURROUNDING AREA

Convention Bandung 2004 (CB2004)
The 33rd Annual Convention & Exhibition 2004

Indonesian Association of Geologist
Horizon Hotel, 29-30 Nov, 1 Oct 2004, Bandung

EARTHQUAKE HAZARD AND RISK
ZONATIONS OF THE SUMATERA ACTIVE
FAULT (SEGMENT SIANOK),
BUKITTINGGI AND SURROUNDING AREA

A. Soehaimi *, A. Djuhanda*, I.Effendi*,
I. Haryanto**, Ismawan**, Y. Fikri**
* Puslitbang Geologi Bandung, ** Jurusan Geologi Unpad
Abstract

The geology of Bukittinggi and surrounding area can be divided into 4 rock
groups: the Pra-Tertiary (metamorphic carboniferous sediment rock, ultra mafic
rock), The tertiary (granite intrusion), The Quartenary (volcanic rock), The
Holocene groups (alluvium and collovium deposits).

The structural geology (studied) in this region consist of 7 faults, there are: The
Sumatra Right Lateral Strike Slip Fault, The Padang Laweh Oblique Fault, The
Gaduik Right Lateral Strike Slip Fault, The Matur Thrust Fault, The Padang
Panjang Thrust Fault, The Simabur Normal Fault, The Tanjung Sawah Normal
Fault.

The displacement rate of river and layer of rocks along the Sumatera Fault
during ± 10.000 years (Marapi and Singgalang volcanic rocks age), The
Sumatera fault can be classified into the A Class active fault base on the
Matsuda's active faults criteria (1973). The maximum intensity base on
Watabe's method (1973) at Bukittinggi and Padang Panjang are VII-VIII MMI
(7.43-7.46 MMI).

The peak ground acceleration base on Murphy-O'Brien's and Kanai's method
using the 1926 Padang Panjang and 2004 Batipuh eatrhquake data showed the
Bukittinggi has peak ground acceleration 394.44 gal and 112.9 gal, while in
Padang Panjang has peak ground acceleration 486,3 gal and 177,87 gal.

Base on the geological condition, seismicity and infrastructure analysis, this
region can be divided into 6 earthquake hazard and risk zones, there are: The
High Hazard and Risk IA and IB Zones, The Intermediate Hazard and Risk IIA
and IIB Zones, The Low Hazard and Risk IIIA and IIIB Zones.