|REVIEW OF THE MS NHESS-2020-395 BY LAHCENE AND CO-AUTHORS|
The paper by Lahcene and co-authors develops empirical tsunami fragility curves for building stocks damaged by the 2018 Anak Krakatau, the 2018 Sulawesi-Palu and the 2004 Indian Ocean events. The paper is a timely and important contribution to the understanding of the tsunami impact on coastal buildings in a region suffering from both seismic and non-seismic tsunamis, and the presented material is thus deemed to be suitable for publication in NHESS with an international appeal.
As the manuscript already underwent one round of review, it is worth mentioning that the authors made a great effort in addressing the reviewers’ comments and accordingly inserted their suggestions and corrections. Overall, the paper reached an acceptable form but, in my opinion, is still need some additional work to be accepted for publication. In particular some sentences need rephrasing, some statements require explanation and revision, equations to be checked and figures need to be reworked.
Specific comments including editorial suggestions:
P1,L23, change “of both tsunamis” to “of these two tsunamis”
P1,L25, change “for each event” to “for both events”
P1,L41-42: the sentence “These tsunamis are likely to cause greater damage due to surrounding areas affected by prior damage due to ground shaking and/or liquefaction” requires rephrasing, please try: “These tsunamis are likely to cause greater destruction as they can follow prior damaging earthquake ground shaking and/or liquefaction”
P2, L43: the sentence “The tsunamis also tend to have longer wave periods attacking the coast” is unclear as all tsunamis cause long waves.
P2, L46: add “a” before ”strong”
P2,L47: In the sentence “This megathrust earthquake was the second largest ever recorded (wave period ranging from 20 to 50 min) (Løvholt et al., 2006)” the authors recall that the Indian Ocean events was the 2nd largest recorded earthquake while they refer to the tsunami periods to support that. This sentence needs rephrasing because tsunami metrics cannot be used in such a way to infer the earthquake intensity.
P2,L48: add “of” before ”Asian”
P2,L51: replace “one” by “tsunami waves”
P2,L53: change “a short” to “a relatively short”
P2,L59: change “loss property” to “loss to property” and cite Omira et al. 2019 paper on the field Plu post-tsunami field survey.
P2,L60-61: the sentence “The Sulawesi 60 earthquake (𝑀𝑤= 7.5) occurred along the Palu-Koro strike-slip fault, 50 km northwest of Palu-Bay” needs revision as the earthquake was initiated outside the Palu-Koro fault and only partially ruptured it (see Socquet et al. 2019 papers among others).
P2,L65-67: Also the sentence “So far, the main hypothesis is that the 65 horizontal displacement of the fault triggered a massive submarine landslide inside Palu-Bay, responsible for the main tsunami.” needs substantial revision as there are, in my opinion, more plausible hypotheses of the tsunami generation (coastal landslides, horizontal coseismic deformation, combination of coastal landslides and coseismic deformation …) than “a massive submarine landslide” that should be easily identifiable from the post-event bathymetric survey (Frederik et al., 2019).
P2,L68: the reference to Heidarzadeh et al. 2018 is not adequate here.
P2,L71: omit “new” before “measure”, “recently developed/proposed” could fit better?
P3,L93: replace “…..poorly understood” by “…., remaining less understood”.
P3,L97: change “with the curves of the 2004 IOT” to “to those derived for the 2004 IOT”
P4,L108: start a new sentence after “events”: These databases ….
P5,Section 2.1 and Table 1: It is not clear to me how two different damage states “Minor” and “Moderate” can be gathered in one unique “Ds1”. According to Suppasri et al.’s 2019 classification the “Minor damage” corresponds to no significant structural or non-structural damage with possibility of building use after minor floor and wall clean up, while the “moderate damage” refers to non-structural damage with use after moderate repairs, which indicates the large difference between the two damage states. The authors must provide plausible justification of such a merging.
P7, Equation 7: the authors presented the hydrodynamic (drag) force and stated that the terms u stands for the maximum current velocity, and D for the maximum inundation depth. However in the drag force the term to be considered is the maximum of the combination u^2*D representing the momentum flux per unit mass, which is different from (u(max))^2*D(max) used by the authors (See Yeh 2007- Design Tsunami Forces for Onshore Structures). This difference can lead to incorrect results and the authors must provide explanation on the way they used the tsunami hydrodynamic force.
P13, Table 3: It is unclear how the volumes of the landslides are estimated.
For both Anak-Krakatau and Palu tsunamis, the authors are asked to present not only the inundation maps but also the results of tsunami generation depicting snapshots of landslide downslope dynamics and generated waves.
Add the geographical coordinates for all the maps.
No need for numbers 1, 2 and 3 in Fig.a instead replace by (b), (c) and (d), respectively.
Change the colour of “Sunda Trench” to be easily readable.
The orange rectangle in Fig. c doesn’t show “Anak Krakatau” but the 4 Islands formed after the 1883 Krakatau eruption.
Add a reference to the 2018 Palu earthquake epicentral location.
The same as for Figure 1: Add the geographical coordinates for all the maps.
No need for numbers 1, 2 and 3 as they refer to Figs. (b), (c) and (d), respectively.
Add the geographical coordinates for all the maps.
The same as for Figure 5.