EERI Preliminary Notes on Tsunami Informa- tion and Response:

Tsunami Generated by MW7.5 , on 28 September 2018

Compiled by Jason R. Patton, Rick Wilson, Lori Dengler, Yvette LaDuke, and Kevin Miller

February 2019 A product of the EERI Learning from Program

1 I. Executive Summary and Key Recommendations

On 28 September 2018 an earthquake with magnitude (M) 7.5 occurred in the Sulawesi region of Indonesia. Minutes after the earthquake, a tsunami hit the coasts within Bay. The tsunami, which was generated immediately after the earthquake, caused significant loss of life in the area. The tsunami was captured in a number of videos, was measured on tide gauges, and appeared to have run-up elevations up to 9 meters (the elevation of the ground surface at the position of maximum inundation distance). During the earthquake, landslides up to several square-kilometers in size were trig- gered by soil liquefaction along the floor of Palu Valley on gently sloping alluvial fans. There is also extensive evidence for landslides along the coastline of . All earthquake- and tsunami-related hazards contributed to the significant structure and infrastructure damage and casualties in the area. Although scientific and engineering analyses are still on-going, initial evaluations were completed and summarized in this report. The following studies and information contributed to the content of this report: • Pre- and post-earthquake remote sensing data have been used to estimate the ground deformation from the earthquake. • A collaboration between the Indonesian Government and Japanese tsunami experts (from a variety of universi- ties) have produced a summary report from their field investigation of tsunami inundation and size. • Landslide experts produced initial assessments and interpretations of the landslides in Palu Valley. To date, there are multiple hypotheses that attempt to explain the triggering source for the multiple tsunamis observed in Palu Bay: • The strike-slip fault motion on the seafloor could have caused horizontal and vertical offsets of submarine bathy- metric features, leading to displacement of the water in the Bay. • The coseismic vertical land motions from the earthquake could have displaced land around the bay. • Multiple slope failures (landslides) along the coastline could have generated direct tsunami waves. • Large submarine landslides could have caused significant seafloor displacement. From initial evaluations, it appears that all of these features could have contributed to tsunami generation, with the subaerial and submarine landslides being the major contributors. The linear shape of Palu Bay likely also contributed to amplification of tsunami waves, especially at the far south end of the bay (Palu City) where there was a higher number of casualties. From a notification standpoint, Indonesia has a large network of tide gauges which are telemetered (e.g. connected via radio or cell communication protocols) and post the data online in real time. If these gauges were incorporated into a tsunami early warning system, it is possible that some people could be notified in advance of tsunami inundation. As with most tsunami events, the significant natural tsunami warning sign is the earthquake shaking itself. This event demonstrates that no matter the perceived tsunami threat, educating coastal populations (residents and visitors) about tsunami hazards should be a priority. These two tsunamis (28 September 2018 Donggala-Palu and this 21 Decem- ber 2018 Sunda Strait event) in Indonesia causing significant casualties demonstrate a need to address non-subduc- tion-earthquake-caused tsunami education and alert/notification solutions.

2 II. Purpose of Report

The 28 September 2018 MW7.5 Sulawesi, Indonesia earthquake, landslides, and tsunami have caused over 2,100 fatal- ities, 680 missing people, 4,600 injuries, and about 79,000 internally displaced persons according to the International Tsunami Survey Team Palu (ITST, 2018). The Earthquake Engineering Research Institute (EERI) supports gathering and sharing information about the effects and damage caused by tsunamis as well as the lessons learned about tsunami notification, evacuation and response activities. This report summarizes the initial observations and response outcomes of the tsunami generated by the

MW7.5 Sulawesi, Indonesia earthquake on September 28, 2018 (Figure 1). Although EERI-related field teams were not deployed specifically for the tsunami, this report provides information compiled by the authors from various references, colleagues, and their own personal experiences during and after the event. The information presented should be consid- ered preliminary; for updates, the authors recommend readers visit the scientific and emergency management websites discussed herein.

Figure 1. Plate tectonic map of , Indonesia. The Palu-Koro and Matano faults are shown on the left (Bellier et al., 2001), as they may be related to several other fault systems trending from the southeast of this region. The USGS epicenter is shown as a red star. On the right is a larger scale map from Watkinson and Hall (2017) that shows some details of the faulting in the Palu Valley. Note their interpretation that includes strike-slip and normal faulting.

3 The authors who compiled this information include: 2. Discussing potential lessons learned and future im- provements for tsunami-related scientific research, • Jason R. Patton, Engineering Geologist, California engineering, notification and response (NOTE: Geological Survey (CGS) discussion about lessons learned represent the • Rick Wilson, Senior Engineering Geologist, Califor- opinions of the authors). nia Geological Survey (CGS) • Lori Dengler, Professor of Geology (Emeritus), III. Earthquake Rupture, Landslides, Humboldt State University and Tsunami Effects • Yvette LaDuke, Tsunami Program Coordinator, California Governor’s Office of Emergency Services The MW7.5 earthquake occurred on 28 September 2018 (Cal OES) at 10:02:45 UTC near Palu, Sulawesi, Indonesia. This event • Kevin Miller, Earthquake, Tsunami, and Volcano had extensive effects including ground shaking, landslides, Program Manager, California Governor’s Office of liquefaction, and tsunami inundation. The earthquake was Emergency Services (Cal OES) the result of slip on the Palu-Koro fault, a sinistral (left-lat- eral) strike-slip plate boundary fault system (Figure 1). Su- lawesi is bisected by the Palu-Kola / Matano fault system. The authors’ objectives for this paper include: These faults appear to be an extension of the Sorong fault, the sinistral strike-slip fault that cuts across the northern 1. Summarizing the background on the earthquake part of New Guinea. and the characteristics of the tsunami that was produced. GPS and block modeling data suggest that the fault in this area has a slip rate of 42 mm/yr (Socquet et al., 2006).

MMI (Intensity) USGS Seismicity I (Not Felt) Magnitude Range 10°N II - III (Weak) 1 - 4 IV (Light) 4 - 5 V (Moderate) 5 - 6 VI (Strong) 0° VII (Very Strong) 6 - 7 VIII (Severe) ° IX (Violent) 7 - 7.5 North 10°S X+ (Extreme) Active Fault (Watkinson & Hall, 2017) A! Tide Gage 110°E 120°E 130°E

ult Palu-Koro fa

Palu ! A City M7.5 MMI VIII PP

MMI VII Donggala

MMI VI

MMI V !

M A

0 12.5 25 50 Miles Topography: SRTM90 Figure 2. Donggala earthquake shaking intensity map, using the Modified Mercalli Intensity scale. North is to the left. USGS M>1 seismicity from September 27 through October 4 is shown. Active faults from Watkinson and Hall (2017) are shown. Pantoloan Port (PP) and (M) tide gage locations are shown.

4 However, analysis of offset stream channels provides evidence of a lower slip rate for the Holocene (last 12,000 years), a rate of about 35 mm/yr (Bellier et al., 2001). Given the short time period for GPS observations, the GPS rate may include postseismic motion from earlier earth- quakes. The seismic hazard associated with this fault was well evi- denced prior to the earthquake (Cipta et al., 2016). Using empirical relations for historic earthquakes compiled by Wells and Coppersmith (1994), Socquet et al. (2016) sug- gest that the Palu-Koro fault system could produce a mag- nitude M7 earthquake once per century. However, studies of prehistoric earthquakes along this fault system suggest that, over the past 2000 years, this fault produces a magni- tude M7-to-M8 earthquake every 700 years (Bellier et al., 2006; Watkinson and Hall, 2017). There is also a record of M>7 earthquakes in the 20th century (Gómez et al., 2000). So, it appears that this is the characteristic earthquake we might expect along this fault.

Earthquake Observations According to the National Disaster Management Authority (Badan Nasional Penanggulangan Bencana, BNPB), there were around 2.4 million people exposed to earthquake Figure 3. (Left) Relative north-south motion across the fault intensity MMI V or greater. MMI V is described as, “Felt by is shown as warm and cool colors. Blue represents motion nearly everyone; many awakened. Some dishes, windows to the south and orange represents relative motion to the broken. Unstable objects overturned. Pendulum clocks north. (Right) Black lines show the localized fault displace- may stop.” However, the highest intensity was observed ments interpreted from a variety of remote sensing meth- near the earthquake source at MMI VIII, which is described ods. The Pantoloan tide gage location is depicted by a blue as “severe” shaking with potential damage to all types of triangle. structures.

Figure 4. Pre- and post-earthquake satellite imagery comparison showing slope failures along the coastline of western Palu Bay, west of the mouth of , Sulawesi, Indonesia (Planet Labs, 2017). We added notations for use in this report. Shoreline outlines are shown for comparison. The largest slope failures are shown with an orange overlay.

5 Figure 2 is a map showing the updated USGS model of sive slope failures in the region. Observations range from ground shaking. This updated earthquake fault slip model “pro-delta” style landslides along the margin of Palu Bay was additionally informed by post-earthquake analysis of to kilometer-scale liquefaction driven lateral-spread type ground deformation. failures that transformed into liquefied flows. Soon after the earthquake, Dr. Sotiris Valkaniotis (Aristotle On 29 September 2018, one day after the event, Carn University of Thessaloniki, Greece) performed an optical (2018) presented on social media a pair of pre- and post- analysis using pixel matching/change detection techniques event images of the shoreline from Planet Labs (Figure 4). and prepared a map that showed large horizontal offsets He discussed the sections of coastline that were missing across the ruptured fault along the entire length of the following the earthquake. Based on our analysis of satel- western margin on Palu Valley (Figure 3). This horizontal lite aerial imagery, the coast of Palu Bay in this area has offset had an estimated ~8 meters (~26 feet) of relative numerous anthropogenic gravel deposits that are placed displacement. InSAR analyses confirmed that the coseis- to allow the gravel mines (the lighter colored region on the mic ground deformation extended through Palu Valley and left of the images) to load gravel on ships. However, some into the mountains to the south of the valley. Note that of these failures occurred in areas not currently being used the fault displacement is greatest along the western Palu as aggregate loading zones and may be locations of man- Valley where the fault enters Palu Bay. Also note how the made fill or natural deposits. inferred location of the fault that slipped is different than Following the 28 September earthquake and tsunami, the the small-scale map of the fault system shown in Figure 1. Copernicus satellite imagery system was activated in the region for emergency response and management. Users Landslide Observations were provided with satellite imagery to evaluate the level of damage visible in the imagery, creating products that The ground shaking from the earthquake led to exten- grade the damage to affected population and assets such

Figure 5. Grading map from Copernicus. Color represents relative damage assessed by using post-event satellite imagery. 6 as settlements, transportation networks, industry, and are the type that generate vertical land motion along the utilities. The mapping products for this event are named sea floor. However, there is historical evidence that strike- AMSR317 and located online here: https://emergency. slip fault earthquakes can also generate tsunamis. For copernicus.eu/mapping/list-of-components/EMSR317. example, the 1999 Izmit, Turkey earthquake (Altinok et al., Figure 5 shows a damage grading map for the region of 1999; Alpar et al., 2003; Gusman et al., 2017; Heidarzadeh southern Palu Bay following the event. The mouth of Palu et al., 2017), and the 2010 M7.0 Haiti strike-slip earth- River is in the center of the map; note the sediment plume quake (Hornbach et al., 2010) generated local tsunamis. in Palu Bay. Red colors represent observations of assets However, these types of earthquakes typically generate believed to be destroyed, orange represents assets that tsunamis that are smaller in size. sustain damage, and yellow represent assets that are pos- sibly damaged. When landslides generate tsunami, they are often localized relative to the location of the landslide. The tsunami size In the grading map (Figure 5), two significant impacts from can be rather large near the landslide and the size dimin- this disaster are observed. First, there is damage along the ishes rapidly with distance from the landslide. An example coastline that diminishes with distance inland away from of a landslide generated tsunami is the 1998 Papua New Palu Bay. This damage is most likely associated with the Guinea tsunami (an earthquake triggered a landslide) tsunami inundation. Second, note the area in the south- causing a “larger than expected” tsunami to inundate the west of the map that is colored red. This is the Balaroa land there. The size of the tsunami was very large near the neighborhood where a large landslide caused the lateral landslide. Localized large tsunami run-up elevations from displacement of roads and several hundred buildings. Two the 1999 Izmit earthquake may also be explained by a sub- much larger kilometer-scale slides are located about 8 and marine landslide source (Altinok et al., 2001). 12 km to the southeast in the Petobo sub-district and the Jono Oge village, respectively. There are also observations and modeling results that sug- gest narrow bays can amplify waves. If the bay is v-shaped, waves can be amplified due to the funnel effect (Shimozo- Tsunami Observations no et al., 2012; 2014). The funnel effect would affect the size of the tsunami in Palu Bay if the source of the tsunami Large, damaging tsunamis are typically associated with were outside of the bay mouth. The modeling of waves subduction zone earthquakes because these earthquakes in narrow water bodies requires special considerations.

7 Figure 7. 50 m long vessel uplifted by the tsunami at Panto- loan Port (Muhari et al., 2018). Figure 6. The map on the left shows the maximum tsunami wave heights along the coastline of Palu Bay and north of tion was provided and given the limited knowledge of the Palu Bay. The color bar shows these heights as color and tsunami wave height or run-up elevation, this model sug- units are in meters. The plot on the right show the wave gested that the slip on the fault may have been sufficient heights at the different locations presented on the map. to explain the size of the tsunami. Note how, in general, The vertical axis is aligned with the map on the left. The the tsunami wave heights increase and appear to be ampli- horizontal axis shows the height in meters. fied to the south. This may have to do with the geometry of the bay relative to the source model. Didenkulova and Pelinsovsky (2011) found that narrow In central eastern Palu Bay, there was a tsunami recorded u-shaped bays can amplify waves if there is a monotonic at the Pantoloan Port tide gauge with a wave height of shallowing of water depth, but the largest waves are about 2 meters (location: “PP” on Figure 2). The larger generated where there are steps in decreased depths. The waves lasted about an hour, but smaller waves (~10-20 cm 2011 Tohoku-oki tsunami also resulted in amplified tsuna- wave height) lasted more than 6 hours. Figure 7 shows a mi waves in narrow bays (Mori et al., 2012). 50m-long vessel that was lifted onto a dock at the port. The Strait, the seaway to the west of Sulawe- The tsunami arrived 6 minutes after the earthquake and si and east of , has the highest frequency of the maximum wave height was measured 2 minutes after historic tsunami in Indonesia (Prasetya et al., 2001). The that (Muhari et al., 2018). Debris lines (marks of debris primary sources are the Palu-Koro and Adang Line-Paster- that represent localized flow depths and wave run-up noster strike-slip fault systems forming the eastern and elevations) were observed to be over 8 meters in places western boundaries, respectively, of the . along the coast and the flow decreased inland (Muhari et However, most of the tsunamigenic earthquakes in this al., 2018). Eyewitness accounts inform us that the tsunami area are attributed to thrust or normal faulting (but the 1927 earthquake mechanism is not known). Nainggolan et al (2015) show that these fault zones have fault strands that include strike-slip, normal, and thrust segments. There are Prasetya et al. (2001) suggest that some tsunamis associated with the Pasternoster fault are likely a result of coseismic landslides (slumping). Table 1 lists the historic tsunamis observed in the Makassar Strait (Prasetya et al., 2001). In the days following the earthquake, Andreas Schäfer pre- pared a numerical simulation of wave amplitude following his methods presented in Schäfer et al. (2017). Bertrand Delouis prepared a slip model, like the initial model devel- Figure 8. 1-minute interval tide gage record from the oped by the USGS. Schäfer used this slip model as a source Pantoloan, Sulawesi, Indonesia. The tide gage is located on of displacement for his tsunami model. Figure 6 shows the the east margin of Palu Bay (Badan Informasi Geospasial, results of this tsunami modeling. At the time this informa- 2018). 8 did not appear to enter Palu Bay from the mouth (e.g. near tides) has a period of about 1 hour and has an amplitude Donggala), but from within the bay itself. of 0.7 m. The short period component, associated with the tsunami, has a period of a few minutes and has an ampli- Figure 8 shows tide gauge data provided by Balai Layanan tude of 3.6 m. Jasa dan Produk Geospasial, who operate the Indone- sia tide gauge network (location: “M” on Figure 2). This Potential Tsunami Source network is presented online at the following website: http://tides.big.go.id:8888/dash/ . The tsunami was also Based on post-earthquake satellite imagery from Digital observed at the Mamuju tide gauge located approximate- Globe, Planet Labs, and Copernicus, the overwhelming ma- ly 275 km to the southwest of the epicenter, along the jority of tsunami damage is localized within Palu Bay. The west-facing coastline in the Makassar Strait. The maximum severity of damage is worse in southern Palu Bay where wave height at Mamuju was about 20 cm, an order of mag- tsunami inundation is on the order of 200-300 meters nitude smaller than recorded at Pantoloan. inland. While at the northern part of the bay, inundation is on the order of 15 meters inland. In the north, most of Sassa and Takagawa (2018) analyzed these tidal data by the buildings that were destroyed by the tsunami were removing the astronomical tide data. They concluded that built over the water, though not entirely. Building damage the long period component (e.g. attributed to astronomical extends further inland in the south where buildings have

Figure 9. Tsunami inundation limits, and splash and run up Figure 10 is another presentation of direct observation of elevations documented in October 2018 (Arikawa et al., tsunami wave run up elevations. This map is a summary of 2018). Inundation height refers to flow depth of the tsuna- direct observations of tsunami flow depths based upon a mi. Splash height refers to the elevation that the tsunami survey that culminated on 5 October 2018 (Meteorologi- wave reached as evidenced by marks on buildings and cal, Climatological and Geophysical Agency, BMKG). other structures. Run-up height refers to the elevation that the tsunami wave reached in certain locations. 9 Figure 11. Observations of tsunami run-up elevations (Omira et al., 2019). been heavily damaged or destroyed. North of the mouth of Figure 10 is another presentation of direct observation of the bay, there is less evidence for tsunami inundation, but tsunami wave run up elevations. This map is a summary of there is localized damage in places. direct observations of tsunami flow depths based upon a survey that culminated on 5 October 2018 (Meteorologi- In the weeks following this natural disaster, numerous cal, Climatological and Geophysical Agency, BMKG). There teams conducted post-tsunami surveys to document the is evidence that narrow water bodies amplify wave heights damage from the tsunami. Their observations included and wave run up elevations (e.g. Didenkulova, 2012) and debris lines and other information that allowed them observations such as those shown in Figure 10 support this to estimate flow depth, run-up heights, and inundation hypothesis. However, other observations presented later distance. Figure 9 is a summary figure showing a subset of in this report suggest that there are other factors that are these observations (Arikawa et al., 2018). These authors controlling the spatial extent of the largest waves. documented areas of potential coseismic subsidence, cliff collapse, and evidence for tsunami inundation height, run- Between 7 and 11 November 2018, a UNESCO team of up height, and splash height (Figure 9). What Arikawa et al. international tsunami scientists conducted a post tsuna- (2018) describe as subsidence is likely their interpretations mi survey in regions that had not been a focus of earlier of the coastline slope failures presented in the satellite post tsunami surveys (Omira et al., 2019). We present imagery earlier in this report. Note how their document- their summary of tsunami run-up elevations in Figure 11. ed tsunami evidence is localized within Palu Bay and the Omira et al. (2019) attribute the variation in run-up eleva- isthmus near the epicenter. Also, note that the tsunami tions due to possible localized non-seismic sources in the observations are associated with evidence of subsidence generation of tsunami waves. These authors also mention (coastline slope failures).

10 Figure 12. Map (left) showing some locations where Sassa and Takagawa (2018) have documented coastline slope failures based on pre- and post-earthquake satellite imagery, labeled A-F. Bathymetric map is from Valkaniotis (2018), made from bathymetry data downloaded from the Indonesian Seamless Digital Elevation Model and National Bathyme- try (DEMNAS) http://tides.big.go.id/DEMNAS/. The shape of the bathymetric contours provide bathymetric evidence for several km-scale landslide scarps, especially on the eastern margin of the Bay (we annotate landslide headscarps with yellow lines). Two low-angle oblique images (right), taken by passengers on a commercial flight out of Palu City, show tsunami waves propagating from the coastline. Area F is the same area shown in in Figure 4 that experienced shoreline slope failures. that tsunami observations of run-up height were an order houses. This occurred for 3 successive days following the of magnitude lower outside of Palu Bay (Table 2 in Omira earthquake. This apparent coseismic subsidence may be et al., 2019). evidence for coseismic vertical land motion, but also could be due to slope instability (similar to the pro-delta type In addition to tsunami and coastal landslide observations slope failures observed along the coastline of Palu Bay). If made by Omira et al. (2019), they also found evidence for due to tectonic vertical land motion, this information could coseismic subsidence. For example, in Balaesang (village be important to unravelling the mystery of the tsunami located at the isthmus near the epicenter, north of Palu triggering. Bay) there was no tsunami damage nor evidence of inun- dation. However, eyewitnesses noted that there was an Figure 12, left side, is a map showing the areas where Sas- increase in relative sea level that led to flooding of their sa and Takagawa (2018) have documented coastline slope 11 failures using Digital Globe satellite imagery as part of the onshore, it should not be ruled out that a larger submarine Open Data Program (Digital Globe, 2018). The coastline landslide is the potential trigger for the tsunami that inun- slope failures shown on Planet Labs imagery (Carn, 2018; dated the southern shores of Palu Bay. Figure 4) are from the area labeled “F” in Figure 12. Ulrich et al. (2019) conducted a physics-based modeling Passengers on the final flight out of the airport in Palu, approach to resolve the spatial distribution of slip includ- prior to the airport being closed due to earthquake dam- ing the time history and sense and magnitude of slip on age, took photos of the tsunami waves sourced from these the fault. Their modeling was calibrated using observations coastline slope failures. Sassa and Takagawa (2018) present from seismic stations, as well as with a comparison with some annotated low angle oblique images posted on social InSAR analysis of surface displacement. Their model incor- media as taken from this air flight. porates rupture dynamics, seismic wave propagation, and tsunami propagation and inundation. They found that the The tsunami waves shown in F may be due to the shoreline 65° east-dipping fault slipped 6m in a left lateral sense and slope failures documented by Carn (2018) using Planet included 2m of normal slip. Ulrich et al. (2019) determined Labs imagery and documented by Sassa and Takagawa that the vertical motion across the fault would have re- (2018) using Digital Globe satellite imagery. sulted in seafloor displacements of 1.5 m (Figure 13). The Sassa and Takagawa (2018) found that the tsunami inun- wave amplitudes and periods from their tsunami modeling dation height was ~3-4 m on average in Palu Bay and was match tide gauge observations at Pantoloan Port. While as high as 6.8 m in localized areas (6.2 m above the astro- landslides were observed onshore and along the coastline, nomical tide at the time of the earthquake). Based on field Ulrich et al. (2019) suggest that the observed tsunami may evidence and their tide gauge analysis, Sassa and Takaga- have been primarily caused by fault displacement. Howev- wa (2018) find that 16% of the tsunami amplitude may er, the single largest limitation of the tsunami modeling of be attributable to large-scale tectonic processes like the Ulrich et al. (2019) is the low resolution of the bathymetry earthquake (such as ground shaking induced slope failure, used. vertical land motion, or fault rupture), while the remaining Figure 13 is a figure from Ulrich et al. (2019) that shows 84% of the tsunami amplitude is most likely due to the their estimate for the surface displacement along the sea- coastline and submarine slope failures mentioned in this floor in Palu Bay. report. A similar coastline slope failure occurred in Haiti in 2010, which is thought to be what caused the local tsu- Figure 14 shows the maximum run-up elevations at select- nami there (Hornbach et al., 2010). However, in Palu Bay, ed locations at Palu Bay as modeled by Ulrich et al. (2019). these coastline slope failures are common and evidently The locations labeled on this map are correlated to the triggered numerous tsunamis (Sassa and Takagawa, 2018). run-up heights bar chart in Figure 15. However, given the kilometer-scale landslides observed

Figure 13. (a) A “snapshot” showing the vertical land motion (Δb in meters) at 50 seconds into their simulation. (b) West- East profiles of the seafloor at -0.7 (red), -0.8 (orange), -0.75 (green), and -0.85 (blue). (c) The step in bathymetry as a function of latitude. The gray dashed line represents the average (from Ulrich et al., 2019).

12 Figure 14. Simulated run-up maxima at various locations where tsunami run-up elevations have been directly observed (from Ulrich et al., 2019).

Figure 15. Comparison between maximum run-up observed elevations (blue) with simulation (orange). Locations are shown on map (Figure 14) and, from left to right, encircle the bay from the northwest, to the south, and then to the northeast (from Ulrich et al., 2019). 13 Figure 15 is a comparison plot showing the simulated run- The following is the timeline translated from Indonesian up elevations and the observations of run-up elevations. into English (using Google translate to start with): There are several limitations to this modeling approach, such as the coarse bathymetry resolution, which greatly 17:02 The earthquake happened. reduces the ability to consider local effects like the ob- 17:07 High alert-level tsunami early warning served coastline slope failures. Thus, at the time of this (0.5-3 m high) in Palu (evacuation). publication, there is insufficient information and analysis to be able to resolve the source(s) of the tsunami (Sassa and 17:10-17:13 Tsunami arrival time. Viral video of the tsu- Takagawa, 2018 versus Ulrich et al., 2019). There does not nami in Palu at dusk (but still daylight) with appear to be a systematic increase in wave size relative to duration ± 3 minutes and confirmed with a distance from the mouth of the Bay, suggesting the wave statement that the tsunami struck shortly size was not amplified significantly by shape of Palu Bay. after the big earthquake. 17:27 Tsunami observed in Mamuju. The moni- tored tide gauge results show the tsunami IV. Emergency Notification and Re- height is 6 cm. The tsunami is not signifi- sponse cant. 17:36 The end of the tsunami. The end of the As previously stated, the tsunami arrived a number of tsunami was completed at 18:36 [17:36] locations within minutes of the earthquake. This allowed local time. very little time for official tsunami alert messages to be- re ceived and the public to react. Figure 16 shows the official timeline of the earthquake and tsunami events according Below are some questions that we have been unable to to BMKG. answer. • Did people evacuate the coastal area after they felt the earthquake? • Did people start to evacuate when they saw the tsunami? • Were there any sirens or other notification devices that went off/sounded? • Did electricity or phones work immediately after the earthquake? • Did people get the message that no tsunami was expected, eight minutes after the earthquake? Below are some of the bulletins and other informational resources prepared in response to the tsunami. • Indonesia National Tsunami Warning Center - Mete- orological, Climatological and Geophysical Agency of Indonesia (BMKG)

o Event Summary (Bahasa Indonesia ) http:// itic.ioc-unesco.org/images/stories/list_ Figure 16. Official timeline of events as presented by of_tsunamis/2018/28sep2018_Indonesia/ BMKG. BMKG_Gempabumi_Tektonik_M7.7_Kabupat- en_Donggala_Sulawesi_Tengah_pada_hari_Ju- mat_28_September_2018_Berpotensi_Tsuna- mi___BMKG.pdf (PDF, 5.12 MB)

14 o Press Release (English, translated from Bahasa 2. Strike-slip tsunami scenarios for known faults Indonesia, M. Yamamoto, A. Kodijat) http:// should be incorporated into probabilistic tsunami itic.ioc-unesco.org/images/stories/list_of_tsu- hazard analyses. namis/2018/28sep2018_Indonesia/BMKG_ PressRelease_2018_Sep_28_Indonesia_pdf. 3. Tsunami bulletins should not be cancelled prior pdf (PDF, 559 KB) to eyewitness observations or some other direct observations can be made in the region of interest. • Indian Ocean Tsunami Service Providers - Public Bulle- tin 4. Tsunami Early Warning systems could be tied to tide gauges, especially in places with existing tide o Meteorological, Climatological and Geo- gauge infrastructure, like Indonesia. physical Agency of Indonesia (BMKG) http:// rtsp.bmkg.go.id/publicdetail.php?even- 5. Tsunami traveling through narrow water bodies tid=20180928171136 (Website) may have amplified waves and amplified tsunami runup. • Pacific Tsunami Warning Center (PTWC) forecast (RIFT model, WCMT earthquake source, 15 arc-sec bathy) Tsunami Warning Notifications o Deep-ocean Amplitude http://itic.ioc-un- esco.org/images/stories/list_of_tsuna- Application of Lessons Learned to Other Regions mis/2018/28sep2018_Indonesia/PTWC_Deep- The InaTEWS-BMKG public tsunami bulletin (Appendix A) Ocean_20180828_max_amp1.jpg (JPG, 94 KB) stated, “Based on historical data and tsunami modelling, o Coastal Amplitude Forecast http://itic. this earthquake is not capable of generating a tsunami ioc-unesco.org/images/stories/list_of_tsuna- affecting the Indian Ocean region. No further bulletins mis/2018/28sep2018_Indonesia/PTWC_Coast- will be issued unless the situation changes.” The official al_20180828_coastal_amp1.jpg (JPG, 91 KB) timeline mentions the tide gauge data from Mamuju, but there is no mention of the tide gauge at Pantoloan Port, which do show a large tsunami wave. It is possible that the V. Lessons Learned and Future Ap- tsunami bulletin should not have been cancelled. plications The public was possibly the most successful participant in spreading information about a potential tsunami as evidenced by a social media video recording, showing Observations of damage and response to the MW 7.5 28 September 2018 earthquake and tsunami provide lessons someone atop the Palu Grand Mall (a multi-story struc- for scientists, engineers, planners, and emergency manag- ture facing north towards Palu Bay, approximately 1.5 km ers. These lessons can improve responses to future disas- west of the yellow Palu River Bridge IV) shouting to people ters. Some of these lessons and some recommendations below to evacuate to higher ground. There are many addi- are provided in this chapter. tional occurrences of people evacuating in response to the ground shaking from the earthquake. It is recommend that potential follow-up actions for federal agencies be addressed through the U.S. National Tsunami The nature of the earthquake (strike-slip) was likely the ba- Hazard Mitigation Program (NTHMP) Warning and Coor- sis of reasoning for the statement, “…this earthquake is not dination Subcommittee, which has served as an effective capable of generating a tsunami affecting the Indian Ocean discussion forum to inform the NTWC and PTWC of issues region.” However, strike-slip earthquakes have a history of of concern to states and territories following events. generating tsunami. Notable examples include the 1999

MW 7.6 Izmit Turkey earthquake, the 2010 MW 7.0 Haiti

earthquake, the 2012 MW 8.6 Wharton Basin earthquake

Tsunami Science and Engineering (Duputel et al., 2012; Wang et al., 2012), and the 2016 Mw 7.8 Wharton Basin earthquake (Heidarzadeh et al., 2017). Potential lessons about tsunami science and engineering from this event: Strike-slip earthquakes are often not considered tsunami- genic because the sense of motion generally does not pro- 1. Strike-slip fault systems can produce deadly and duce much coseismic vertical land motion. For example, devastating tsunamis (e.g. over 2,200 fatalities for we can compare tsunami models produced in real-time the 28 September 2018 MW 7.5 earthquake and following the 2012 MW 8.6 Wharton Basin earthquake to tsunami). see how tsunami size is affected by vertical land motion for

15 thrust relative to strike-slip earthquake motion. As we con- coseismic subsidence may not happen during each earth- tinue to learn more about strike-slip earthquakes, we make quake in this area, we may surmise that this has happened observations that there is indeed sometimes a portion of at least once in the past, so is possible that this may occur slip that produces vertical land motion. This may be the again the future. case for the 2018 Sulawesi earthquake, as evidenced by the analysis by Ulrich et al. (2019). The 23 January 2018 Gulf of Alaska earthquake is also thought to have produced vertical land motion across

Application of Lessons Learned to the USA multiple faults (Lay et al., 2018). This MW 7.9 earthquake sequence was the result of slip on intraplate faults in the There were no tsunami warning notifications from the Pacific plate, possibly due to reactivation of spreading NTWC, PTWC, or any other federal or state agency because ridge and fracture zone structures related to the formation this event was not within their geographic area or respon- of the oceanic lithosphere. Lay et al. (2018) suggest that sibility for notification. there may have been as much as over 2 m of vertical land motion along the northwestern striking fault and about 0.2 m of vertical land motion along the northeast striking Tsunami Response faults. Based on their comparison with DART buoy water Application of Lessons Learned to Other Regions surface elevation data, the northwestern striking fault ap- pears to be the principal locus of slip and source of vertical Following the 2004 -Andaman subduction zone land motion responsible for the tsunami waves. However, MW 9.1 earthquake and tsunami, killing about a quarter of as they state, there are no direct observations of coseismic a million people, the nation of Indonesia has made great ground displacement along the seafloor. progress in educating the public about the hazards associ- ated with earthquakes and tsunami. The people along the The state of California is traversed by the San Andreas coast know that tsunamis are associated with earthquakes. fault, a dextral strike-slip plate boundary fault system. There are several faults that join the SAF to accommodate Evident on social media postings of videos before, during, relative Pacific – North America plate motion. As these and after tsunami inundation, many people knew to faults interact and are oriented oblique to relative plate evacuate to higher ground. However, there is some video motion, additional faults form with normal and reverse/ evidence that people, who were safely atop a multi-story thrust motion. Offshore, any of these faults may serve as a building, evacuated downwards to the ground surface. Be- potential source for local tsunami hazard along the coast- cause the tsunami did not inundate more than 200-300 m line. Below are some examples. in this location, these people probably survived. However, other scenarios might end with different results. In northern CA, the San Andreas and San Gregorio are known Holocene (<12,000 years) active faults that strike Application of Lessons Learned to the USA offshore of the San Francisco Bay area, along Tomales Bay Many people associate tsunami with subduction zones as (similar in shape, but not depth, to Palu Bay), and between they cause earthquakes that most commonly trigger tsuna- Point Reyes and Shelter Cove. Recent work from Beeson mi. Given what we have learned since at least 1999, strike- et al. (2017) has constrained the northern terminus of slip earthquakes can produce deadly tsunami. In the case the San Andreas fault to extend onshore but not offshore, of the 1999 Izmit Turkey earthquake and tsunami, almost north of Shelter Cove. They also found that there is poten- 200 fatalities resulted from a tsunami with an average tial for vertical separation across the fault north of Point wave height of more than 2 m (Altinok et al., 1999, 2001). Reyes as evidenced by fault bounded sedimentary basins observed in seismic reflection data. Future ruptures on this There are also strike-slip earthquakes in the US that have segment of the San Andreas fault should be considered as generated tsunami, including the 1906 MW 7.9 San Francis- potential for tsunamigenesis. co earthquake (Geist and Zoback, 1999, 2002) and the 23 Koehler et al. (2005) found lithostratigraphic and biostra- January 2018 MW 7.9 Gulf of Alaska earthquake (Wilson et al., 2018). The 1906 San Francisco earthquake very likely tigraphic stratigraphic evidence for prehistoric coseismic generated a small-sized tsunami because of a dilatational vertical land displacement (subsidence) associated with fault step over along the San Andreas fault caused coseis- the northern San Gregorio fault in Half Moon Bay, Cali- mic subsidence of the seafloor (Geist and Zoback, 2002). fornia. These authors found structural evidence of earth- Ryan et al. (2008) found sedimentary stratigraphic and quakes in fault trenches that shows these deposits formed structural evidence of a long prehistory of this vertical land synchronously with earthquakes on the San Gregorio fault. motion, inferred from Plio-Pleistocene subsidence rates It seems reasonable that the offshore sections of this fault calculated from offshore seismic reflection data. While

16 system may also be capable of generating coseismic verti- where tide gauge based TEW may have helped (especially cal land displacement. given the lack of an earthquake that would have produced a natural warning). There are known faults offshore of Monterey Bay that, if displaced, could be sources for tsunami (Greene, 1990). Johnson et al. (2016) show in seismic reflection profiles highly deformed Pleistocene sediments associated with VI. Acknowledgements the San Gregorio fault system. We would like to thank the people who provided their In southern California, there is an extensive network of near-real time evaluations and analyses of this disaster faults in the California Borderlands. Many of these faults as it was unfolding, largely on social media. This sharing are reverse faults, but there are some notable strike slip of information was key to our ability to respond to this systems. The best known is the Rose Canyon / Newport-In- natural disaster. Hopefully people continue to share their glewood fault, probably responsible for the 1933 Long results freely online and that people continue to respect Beach earthquake. Recently collected seismic reflection the sources of these analytical results. We have attempted data provide details about the geometry of this fault sys- to give credit to the sources we used in this report. tem offshore of San Onofre (Sahakian et al., 2017). These authors interpret that multiple fault strands include several step-overs, which is evidence that these faults could Additional Sources Online: produce vertical ground displacement. These faults need Discover Magazine: to be considered as potential sources for tsunamigenesis given our knowledge about historic earthquakes, but also • 2018.09.28 Violent Tsunami Strikes Palu in Indone- evidenced by the 28 September 2018 Donggala-Palu strike- sia http://blogs.discovermagazine.com/rockyplan- slip earthquake and tsunami. et/2018/09/28/violent-tsunami-strikes-palu-in-in- donesia/#.XL5X6TBKhaQ Tsunami Early Warning and Public Notification Temblor Articles: The agencies in Indonesia failed to maintain a warning for people along the coast of central Sulawesi. There was an • 2018.09.28 The Palu-Koro fault ruptures in a initial bulletin, but this was canceled due to the nature of M=7.5 quake in Sulawesi, Indonesia, triggering a the earthquake (strike-slip) and due to the low amplitude tsunami and likely more shocks http://temblor.net/ wave recorded on the Mamuju tide gauge. However, it is earthquake-insights/the-palu-koro-fault-ruptures- currently unclear why these agencies did not utilize the in-a-m7-5-quake-in-sulawesi-indonesia-triggering- information from the Pantoloan Port tidal data, was opera- a-tsunami-and-likely-more-shocks-7797/ tional at the timeFigure ( 8). It would have been prudent to • 2018.10.03 Tsunami in Sulawesi, Indonesia, trig- extend the time period of the initial tsunami bulletin for a gered by earthquake, landslide, or both http:// period of several hours. temblor.net/earthquake-insights/tsunami-in-su- The nation of Indonesia operates one of the largest sys- lawesi-indonesia-triggered-by-earthquake-land- tems of tide gauges in the world. Some gauges are already slides-or-both-7825/ connected to the Indonesian Tsunami Earthy Warning • 2018.10.16 Coseismic Landslides in Sulawesi, System (Schӧne et al., 2011). These tide gauges provide a Indonesia http://temblor.net/earthquake-insights/ unique opportunity to developing a tsunami early warning coseismic-landslides-in-sulawesi-indonesia-7874/ system to augment the currently inoperable and expen- sive tsunami buoy system. For example, if a tsunami early Earth Jay Reports: warning system (TEW) were tied to these tide gauges, an alert could have been broadcast immediately following • 2018.09.28 M 7.5 Sulawesi http://earthjay. when the wave was recorded at the Pantoloan gauge com/?p=7793 . (Wӓchter et al , 2012). If this TEW system were tied to SMS • 2018.10.16 M 7.5 Sulawesi UPDATE #1 http:// (mobile phone messaging), it is possible that a notification earthjay.com/?p=7866 could have been sent to people in Palu City prior to the arrival of the tsunami (presuming Pantoloan Port was be- tween the tsunami source and Palu City). A recent tsunami in the Sunda Strait, probably a result of the collapse of Anak Krakatau (Patton et al., 2018), is another example of

17 Twitter accounts Involved in the response to this sequence Carn, S., 2018. “Significant damage to coastline NW of #Palu of disasters: #Sulawesi (near 0.8ºS, 119.8ºE) seen in these @planetlabs imag- es from Sept 28 and 29. #PaluTsunami (Images Copyright 2018 • ASEAN Coordinating Centre for Humanitarian As- Planet Labs Inc.)” [twitter post] https://twitter.com/simoncarn/ sistance on disaster management https://twitter. status/1046248107556696064 com/AHACentre Cipta, A., Robiana, R., Griffin, J.D., Horspool, N., Hidayati, S., and • BMKG Indonesia https://twitter.com/infoBMKG Cummins, P., 2016. A probabilistic seismic hazard assessment for Sulawesi, Indonesia in Cummins, P. R. &Meilano, I. (eds) Geo- • Simon Carn https://twitter.com/simoncarn hazards in Indonesia: Earth Science for Disaster Risk Reduction, Geological Society, London, Special Publications, v. 441, http:// • Andreas M. Schäfer https://twitter.com/CATnews- doi.org/10.1144/SP441.6 DE Didenkulova, I., 2012. Tsunami runup in narrow bays: the case • Sotiris Valkaniotis https://twitter.com/SotisValkan of Samoa 2009 Tsunami in Nat. Hazards, v. 65, p/. 1629-1636, http://doi.org/10.1007/s11069-012-0435-7 • Eric Fielding https://twitter.com/EricFielding Didenkulova, I., and Pelinovsky, E., 2011. Runup of Tsunami • IRIS Earthquake Science https://twitter.com/ Waves in U-Shaped Bays in Pure Appl. Geophys., v. 168, p. 1239- IRIS_EPO 1249, http://doi.org/10.1007/s00024-010-0232-8 • Anthony Lomax https://twitter.com/ALomaxNet Digital Globe Open Data Program. 2018. Satellite images of Palu and Donggala, Sulawesi, Indonesia, Retrieved from https://www. • Sutopo Purwo Nugroho https://twitter.com/Suto- digitalglobe.com/opendata/indonesia-earthquake-tsunami/ . po_PN Accessed 30 Oct 2018 • Dave Petley https://twitter.com/davepetley Duputel, Z., Rivera, L., Kanamori, H., & Hayes, G., 2012. W phase source inversion for moderate to large earthquakes (1990–2010) • Jascha Polet https://twitter.com/CPPGeophysics in GJI, v. 189, no. 2, p. 1125-1147 Geist, E. L., and Zoback, M. L., 1999. Analysis of the tsunami generated by the Mw 7.8 1906 San Francisco earthquakes in Geology, v. 27, p. 15-18 VII. References Geist, E.L., and Zoback, M.L., 2002. Examination of the tsuna- mi generated by the 1906 San Francisco Mw = 7.8 earthquake, Altinok, Y., Alpar, B., Ersoy,Ş ., and Yalҫiner, A.C., 1999. Tsunami using new interpretations of the offshore San Andreas Fault, in th generation of the Kocaeli Earthquake (August 17 1999) in the Parsons, T., ed., Crustal Structure of the Coastal and Marine San Izmit Bay; coastal observations bathymetry and seismic data in Francisco Bay Region, California: U.S. Geological Survey Profes- Turkish J. Marine Sciences v. 5, no. 3, p. 131-148 sional Paper 1658, p. 29-42 Altinok, Y., Tinti, S., Alpar, B., Yalҫiner, A.C., Ersoy, Ş., Bortolucci, Gómez, J.M., Madariaga, R., Walpersdorf, A., and Chalard, E., E., and Armigliato, A., 2001. The Tsunami of August 17, 1999 I 2000. The 1996 Earthquakes in Sulawesi, Indonesia in BSSA, v. Izmit Bay, Turkey in Natural Hazards, v. 24, p. 133-146 90, no. 3, p. 739-751 Alpar, B., Altinok, Y., Gazioǧlu, C., and Yücel, Z.Y., 2003. Tsunami Greene, H.G., 1990. Regional tectonics and structural evolution Hazard Assessment in İstanbul in Turkish J. Marine Sciences v. 9, of the Monterey Bay region, central California in Greene, H.G., no. 1, p. 3-29 Weber, G.E., Wright, T.L., and Garrison, R.E. (eds.) Geology and tectonics of the central California coast region: San Francisco to Badan Informasi Geospasial, 2018. 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M.J., Braudy, N., Briggs, R.W., Cormier, M.H., Davis, The September 28th, 2018, Tsunami In Palu-Sulawesi, Indonesia: M,B., Diebold, J.B., Dieudonne, N., Douilly, R., Frohlich, C., Gulick, A Post-Event Field Survey in Pure and Applied Geophysics, 17 S.P.S., Johnson III, H.E., Mann, P., McHugh, C., Ryan-Mishkin, K., pp., https://doi.org/10.1007/s00024-019-02145-z Prentice, C.S., Seeber, L., Sorlien, C.C., Steckler, M.S., Symithe, S.J., Taylor, F.W., Templeton, J., 2010. High tsunami frequency as Patton J.R., Stein R.S., Sevilgen V., 2018. Sunda Strait tsunami a result of combined strike-slip faulting and coastal landslides in launched by sudden collapse of Krakatau volcano into the sea, Nat Geosci v. 3, p. 783-788 Temblor, http://doi.org/10.32858/temblor.001 ITST, 2018. International Post-Tsunami Survey for the Tsunami Pa- Planet Team, 2017. Planet Application Program Interface: In lu-Donggala, Sulawesi Tengah – Indonesia, 28 September 2018, Space for Life on Earth. 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19 Socquet, A., W. Simons, C. Vigny, R. McCaffrey, C. Subarya, D. Sar- sito, B. Ambrosius, and W. Spakman (2006), Microblock rotations VII. Copyright and fault coupling in SE triple junction (Sulawesi, Indonesia) from GPS and earthquake slip vector data, J. Geophys. Res., 111, © 2019 Earthquake Engineering Research Institute, Oak- B08409, https://doi.org/10.1029/2005JB003963 land, California, 94612-1934 Ulrich, T. Vater, S., Madden, E.H., Behrens, J., van Dinther, Y., van All rights reserved. No part of this publication may be Zelst, I., Fielding, E.J., Liang, C., and Gabriel, A.-A., 2019. Coupled, reproduced in any form or by any means without the prior Physics-based Modeling Reveals Earthquake Displacements are written permission of the publisher, Earthquake Engineer- Critical to the 2018 Palu, Sulawesi Tsunami submitted to -PA ing Research Institute, 499 14th Street, Suite 220, Oakland, GEOPH. https://eartharxiv.org/3bwqa CA 94612- 1934, telephone: +1 (510) 451-0905, email: Valkaniotis, S., 2018. “First, those two for review. Regional [email protected], website: www.eeri.org. bathymetry & bath data from Hall and Palu bay detailed bathym- The Earthquake Engineering Research Institute (EERI) is a etry (depth contours form Geospatial Information Agency BIG)” nonprofit corporation. The objective of EERI is to reduce [twitter post] 06 Oct 2018https://twitter.com/SotisValkan/sta - tus/1048474696013021186 earthquake risk by (1) advancing the science and practice of earthquake engineering, (2) improving understanding of Valkaniotis, S., Ganas, A., Tsironi, V., and Barberopoulo, A., 2018. the impact of earthquakes on the physical, social, econom- A preliminary report on the M7.5 Palu earthquake co-seismic ic, political, and cultural environment, and (3) advocating ruptures and landslides using image correlation techniques on comprehensive and realistic measures for reducing the optical satellite data in report submitted to EMSC on 19 October, harmful effects of earthquakes. 2018 12:00 UTC https://zenodo.org/record/1467128#.XGWy- WlVKhaQ Any opinions, findings, conclusions, or recommendations Watkinson, I.M. and Hall, R., 2017. Fault systems of the eastern expressed herein are the authors’ and do not necessarily Indonesian triple junction: evaluation of Quaternary activity and reflect the views of EERI, the authors’ organizations, or any implications for seismic hazards in Cummins, P. R. & Meilano, I. funding agencies. (eds.) Geohazards in Indonesia: Earth Science for Disaster Risk Reduction, Geological Society, London, Special Publications, v. This publication is available in PDF format from http:// 441, https://doi.org/10.1144/SP441.8 www.eeri.org. Walpersdorf, A., Rangin, C., and Vigny, C., 1998. GPS compared to long-term geologic motion of the north arm of Sulawesi in EPSL, v. 159, p. 47-55 Wang, D., Becker, N.C., Walsh, D., Fryer, G.J., Weinstein, S.A., McCreery, C.S., Sardiña, V., Hsu, V., Hirshorn, B.F., Hayes, G.P., Duputel, Z., Rivera, L., Kanamori, H., Koyanagi, K.K., and Shiro, B., 2012. Real-time forecasting of the April 11, 2012 Sumatra tsuna- mi in GRL, v. 39, L19601, https://doi.org/10.1029/2012GL053081 Wilson, R., Belanger, D., Dengler, L., LaDuke, Y., and Miller, K., 2018. EERI Preliminary Notes on Tsunami Information and Response: Tsunami Generated by MW7.9 Gulf of Alaska Earth- quake on January 23, 2018, a product of the EERI Learning From Earthquakes Program, 20 pp. Zahirovic, S., Seton, M., and Müller, R.D., 2014. The Cretaceous and Cenozoic tectonic evolution of in Solid Earth, v. 5, p. 227-273, https://doi.org/10.5194/se-5-227-2014 Zhu, J., Baise, L. G., Thompson, E. M., 2017, An Updated Geo- spatial Liquefaction Model for Global Application, Bulletin of the Seismological Society of America, 107, p 1365-1385, https://doi. org/0.1785/0120160198

20 VIII. Appendix A – Tsunami Bulletin

The following bulletin was published online by the Indonesia Tsunami Early Warning System (InaTEWS) approximately 8 minutes after the earthquake. http://rtsp.bmkg.go.id/publicdetail.php?eventid=20180928171136

TSP-InaTEWS-20180928-1011-001

------

PUBLIC TSUNAMI BULLETIN NUMBER 1

IOTWMS TSUNAMI SERVICE PROVIDER INDONESIA (InaTEWS-BMKG) issued at 1011 UTC, Friday, 28 September 2018

------

... EARTHQUAKE BULLETIN ...

This bulletin applies to areas within and bordering the Indian Ocean and is issued by Tsunami Service Provider INDONESIA in support of the

UNESCO/IOC Indian Ocean Tsunami Warning and Mitigation System (IOTWMS).

For information applying to areas outside the Indian Ocean refer to the relevant Tsunami Warning and Mitigation Systems listed in section

6 below.

1. EARTHQUAKE INFORMATION

IOTWMS-TSP INDONESIA has detected an earthquake with the following preliminary information:

Magnitude : 7.7 Mwp

Depth : 10km

Date : 28 Sep 2018

Origin Time: 10:02:44 UTC

Latitude : 0.18S

Longitude : 119.85E

Location : Minahassa Peninsula, Sulawesi

2. EVALUATION

Based on historical data and tsunami modelling, this earthquake is not capable of generating a tsunami affecting the Indian Ocean

21 region. No further bulletins will be issued unless the situation changes.

Further information on this event will be available at: http://rtsp.bmkg.go.id

3. ADVICE

This bulletin is being issued as advice. Only national/state/local authorities and disaster management officers have the authority to make decisions regarding the official threat and warning status in their coastal areas and any action to be taken in response.

For more detailed information, please refer to the tsunami advisory bulletins issued by the National Tsunami Warning Centres (NTWCs) of

Indian Ocean countries. The tsunami warning status reported by NTWCs

For their countries can be found at: http://www.incois.gov.in/Incois/tsunami/NTWCFeedbackStatus.jsp

4. OTHER INDIAN OCEAN TSUNAMI SERVICE PROVIDERS:

Other IOTWMS-TSPs may issue additional information at:

IOTWMS-TSP AUSTRALIA: http://www.bom.gov.au/tsunami/iotws

IOTWMS-TSP : http://www.incois.gov.in/Incois/tsunami/eqevents.jsp

5. CONTACT INFORMATION

IOTWMS-TSP INDONESIA:

THE AGENCY FOR METEOROLOGY CLIMATOLOGY AND GEOPHYSICS (BMKG)

InaTEWS - Indonesian Tsunami Early Warning System

Address: Jl. Angkasa I no.2 Kemayoran, , Indonesia, 10720

Tel.: +62 (21) 4246321/6546316

Fax: +62 (21) 6546316/4246703

P.O. Box 3540 Jakarta

Website: http://rtsp.bmkg.go.id/publicbull.php

E-Mail: [email protected]

[email protected]

6. TSUNAMI WARNING SYSTEMS OUTSIDE THE INDIAN OCEAN

Pacific Tsunami Warning and Mitigation System (PTWS):

------

22 Pacific Tsunami Warning Centre (PTWC) http://ptwc.weather.gov/

North West Pacific Tsunami Advisory Centre (NWPTAC) http://www.jma.go.jp/en/tsunami/

US National Tsunami Warning Centre (US NTWC) http://wcatwc.arh.noaa.gov/

Joint Australian Tsunami Warning Centre (JATWC) http://www.bom.gov.au/tsunami/

Northeast Atlantic, Mediterranean and Connected Seas (NEAMTWS):

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French National Tsunami Warning Centre (CENALT) http://www.info-tsunami.fr

Institute of Geodynamics, National Observatory of Athens http://www.gein.noa.gr/en/

Kandilli Observatory and Earthquake Research Institute, Turkey http://www.koeri.boun.edu.tr/2/en/

Caribbean and Adjacent Regions (CARIBE EWS):

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Pacific Tsunami Warning Centre (PTWC) http://ptwc.weather.gov/

END OF BULLETIN

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