The following report contains the description of the impact, damages, and losses due the M7.5 earthquake that occurred at Palu, Indonesia on 28 Sept’18. It also includes description of the process of footprint generation using OpenQuake engine by GEM foundation. Please download the file Palu_earthquake.html and open it in your web browser for proper rendering of the footprints. PLEASE NOTE: The input file for Rmarkdown needs to be generated by OpenQuake first. As it is too large to upload in github, it is excluded here. However, the user can generate it with OpenQuake setup using the files in the folder OQ_input. Please read the OpenQuake documentation first.
A reference footprint for the same can be found in https://www.usgs.gov/news/magnitude-75-earthquake-near-palu-indonesia.
On 28 September 2018, at 10:02:45 (UTC), an (M_W) 7.5 earthquake hit central Sulawesi, Indonesia. The epicenter (0.256S, 119.846E), determined by the United States Geological Survey (USGS), was located about 77 km north of Palu City (Figure 1). This seismic event triggered catastrophic soil liquefaction, landslides, and a tsunami as well. Both the USGS and the gCMT (global CMT: https//:www.globalcmt.org) provided the focal mechanism solutions, which indicated that the earthquake occurred on the north section of the Palu-Koro Fault, a predominantly sinistral fault with a normal component [1].
The September 2018 earthquake likely occurred due to slip on the fast slipping, predominantly strike-slip, NNW trending, Palu-Koro fault at the western boundary of the North Sula block (Figure 1), which forms part of the complex triple junction at the intersection of the Australian, Philippine, and Sunda plates (Figure 1). The fault accommodates up to 40 mm/year of left-lateral motion (with some normal component) due to block rotation. The strain accumulates over many decades or centuries and is released suddenly over a few seconds as the fault slips during the earthquake, causing the ground to shake[6].
This event affects central of Sulawesi and very high impact on Palu city, Donggala, Sigi and Parigi Moutong. At least 2,077 people killed, 4,438 injured, 1,075 missing and 206,524 displaced; at least 68,451 houses damaged or destroyed; bridges and roads damaged; power and telecommunication outages occurred in Sulawesi Tengah from the combined effects of the earthquake, tsunami, liquefaction and landslides. The towns of Balaroa and Petobo were submerged due to liquefaction. A tsunami with an estimated wave height of 7 m was observed at Palu. Damage estimated at 911 million US dollars[2].
Among the damaged structures, most affected were either Non-Engineered Light Timber Construction Frame or Non-Engineered Lightly Reinforced Concrete Construction Frame. Most of the Light Timber Frame buildings simply washed away in the face of the following Tsunami. Non-Engineered Lightly Reinforced Concrete Construction Frame buildings, most of which might not have been as per the accepted codal provisions, also suffered severe to complete damage[3]. Engineered Reinforced Concrete Construction Frame buildings constituted a smaller portion of all structures (4%). In this, the tsunami affected the ground and first floors. Most damage was observed on first floor levels included failure of infill clay brick masonry partitioning between reinforced concrete columns, external doors and windows and electricity and plumbing services.
In Palu City, non-engineered light timber and lightly reinforced concrete construction frame buildings were highly susceptible to non-structural component damage when the tsunami flow depths respectively exceed 0.4 m and 1 m above the first finished floor level. Irreparable or complete damage of construction frame components occurred regularly when flow depths exceeded 1.2 m above first finished floor level. Engineered reinforced concrete construction frame buildings were more resistant, with only non-structural component damage observed for flow depths up to 2.5 m above first finished floor level [3].
Additionally, damage observed to seawalls at Port of Donggala was predominantly caused by the earthquake and subsidence, while tsunami damage to seawall superstructures was observed at Port of Pantaloan[3].
This study uses Chiou and Youngs, 2008 (CY08)[10] model as GMPE. CY08 was developed as part of the Pacific Earthquake Engineering Research Center’s (PEER) Next Generation Attenuation model (NGA) project using PEER-NGA empirical strong motion database that contains 3,551 recordings from 173 earthquakes. This ground motion model was developed to represent free-field motions from shallow crustal earthquakes in active tectonic regions and hence is an appropriate match for the Palu fault mechanism. The data set is also global in nature.
The event footprint was generated using Openquake Software by Global Earthquake Model (GEM). As the current event is already specified, the calculation was done in “scenario” mode for a 2 km grid. A total of 1000 realizations (for aleatoric uncertainty) are generated and the mean footprint is considered.
For a more detailed report with the plot of generated footprint, please check the Palu_earthquake.html file.
Hazard estimation 2km grid Area Source
==========================================
============== ===================
checksum32 3,546,521,487
date 2020-01-04T15:31:57
engine_version 3.7.1
============== ===================
num_sites = 27578, num_levels = 3, num_rlzs = 1
Parameters
----------
=============================== ==================
calculation_mode 'scenario'
number_of_logic_tree_samples 0
maximum_distance {'default': 200.0}
investigation_time None
ses_per_logic_tree_path 1
truncation_level 3.0
rupture_mesh_spacing 2.0
complex_fault_mesh_spacing 2.0
width_of_mfd_bin None
area_source_discretization None
ground_motion_correlation_model None
minimum_intensity {}
random_seed 2997
master_seed 0
ses_seed 42
=============================== ==================
Input files
-----------
============= ========================================
Name File
============= ========================================
job_ini `job.ini <job.ini>`_
rupture_model `rupture_model.xml <rupture_model.xml>`_
site_model `site_data.csv <site_data.csv>`_
============= ========================================
Composite source model
----------------------
========= ======= =============== ================
smlt_path weight gsim_logic_tree num_realizations
========= ======= =============== ================
b_1 1.00000 trivial(1) 1
========= ======= =============== ================
Realizations per (GRP, GSIM)
----------------------------
::
<RlzsAssoc(size=1, rlzs=1)>
Number of ruptures per tectonic region type
-------------------------------------------
============ ====== === ============ ============
source_model grp_id trt eff_ruptures tot_ruptures
============ ====== === ============ ============
scenario 0 * 1 0
============ ====== === ============ ============
Information about the tasks
---------------------------
Not available
Data transfer
-------------
==== ==== ========
task sent received
==== ==== ========
Slowest operations
------------------
====================== ======== ========= ======
calc_66 time_sec memory_mb counts
====================== ======== ========= ======
ScenarioCalculator.run 116 0.0 1
saving gmfs 104 0.0 1
computing gmfs 10 315 1
====================== ======== ========= ======
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Wang, Y., Feng, W., Chen, K. and Samsonov, S., 2019. Source Characteristics of the 28 September 2018 Mw 7.4 Palu, Indonesia, Earthquake Derived from the Advanced Land Observation Satellite 2 Data. Remote Sensing, 11(17), p.1999.
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https://earthquake.usgs.gov/earthquakes/eventpage/us1000h3p4/origin/detail
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Paulik, R., Gusman, A., Williams, J.H., Pratama, G.M., Lin, S.L., Prawirabhakti, A., Sulendra, K., Zachari, M.Y., Fortuna, Z.E.D., Layuk, N.B.P. and Suwarni, N.W.I., 2019. Tsunami hazard and built environment damage observations from palu city after the september 28 2018 sulawesi earthquake and tsunami. Pure and Applied Geophysics, 176(8), pp.3305-3321.
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Stewart, J.P., Douglas, J., Javanbarg, M., Bozorgnia, Y., Abrahamson, N.A., Boore, D.M., Campbell, K.W., Delavaud, E., Erdik, M. and Stafford, P.J., 2015. Selection of ground motion prediction equations for the global earthquake model. Earthquake Spectra, 31(1), pp.19-45.
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Fang, J., Xu, C., Wen, Y., Wang, S., Xu, G., Zhao, Y. and Yi, L., 2019. The 2018 Mw 7.5 Palu Earthquake: A Supershear Rupture Event Constrained by InSAR and Broadband Regional Seismograms. Remote Sensing, 11(11), p.1330.
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https://www.air-worldwide.com/Blog/How-the-Palu-Earthquake-Caused-So-Much-Devastation/
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Ulrich, T., Vater, S., Madden, E.H., Behrens, J., van Dinther, Y., van Zelst, I., Fielding, E.J., Liang, C. and Gabriel, A.A., 2019. Coupled, Physics-based Modeling Reveals Earthquake Displacements are Critical to the 2018 Palu, Sulawesi Tsunami.
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Chiou, B.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), pp.173-215.
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Kaklamanos, J., Baise, L.G. and Boore, D.M., 2011. Estimating unknown input parameters when implementing the NGA ground-motion prediction equations in engineering practice. Earthquake Spectra, 27(4), pp.1219-1235.