Field Survey and Simulation of an Undocumented Tsunami: The 1990 Earthquake, Caspian Sea, Amir Salaree and Emile A. Okal BLANK [email protected] , [email protected] Background Earthquake Source Different Slide Scenarios A B C Tsunamigenic Events in Southern Caspian Sea The Rudbar-Tarom (most commonly known as Rudbar) earthquake, Mw = 7.4, occurred on June 20, 1990 at 21:00:13 49˚ 49.2˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 49˚ 49.2˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 49˚ 49.2˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚

UTC (00:30:13 on June 21, local time). 38˚ 38˚ 38˚ 38˚ 38˚ 38˚ 47˚ 48˚ 49˚ 50˚ 53˚ 54˚ 55˚ 56˚ CMT Single Event Composite Solution Difference 51˚ 52˚ 48.5˚ 49˚ 49.5˚ 50˚ 50.5˚ 51˚ 37.8˚ 37.8˚ 37.8˚ 48.5˚ 49˚ 49.5˚ 50˚ 50.5˚ 51˚ 51.5˚ 52˚ 52.5˚ 48.5˚ 49˚ 49.5˚ 50˚ 50.5˚ 51˚ 51.5˚ 52˚ 52.5˚ 48.5˚ 49˚ 49.5˚ 50˚ 50.5˚ 51˚ 51.5˚ 52˚ 52.5˚ 37.8˚ 37.8˚ 37.8˚ 40˚ 40˚ 38˚ −0.08 38˚ −0.06 −0.04 40˚ 40˚ 40˚ 40˚ 40˚ 40˚ AZERBAIJAN km −0.1 km −0.06 km km km 37.6˚ 37.6˚ 37.6˚ 37.6˚ 37.6˚ 37.6˚ 0 100 TURKMENISTAN −0.08 1895 0 50 39.5˚ 39.5˚ 39.5˚ 39.5˚ 39.5˚ 39.5˚ −0.1 1868 Cheleken 0 100 0 100 0 100 39˚ 1910 39˚ 0.04 37.4˚ 37.4˚ 37.4˚ 37.4˚ 37.4˚ 37.4˚ 39˚ 39˚ 39˚ 0.02 39˚ 39˚ 0.01 39˚ 37.5˚ 37.5˚ 0.01 0.04

−0.1

0 0.06 −0.06 37.2˚ 37.2˚ 37.2˚ 37.2˚ 37.2˚ 37.2˚ 1960(?) C A S P I A N 38.5˚ 38.5˚ 38.5˚ 38.5˚ 38.5˚ 0.08 38.5˚ 0 20 40 0 20 40 0 20 40 0.1 SEFIDROOD −0.25 0.08 38˚ 38˚ −0.02 0.06 0.06 −0.06 0.06 0.06 49˚ 49.2˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 49˚ 49.2˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 49˚ 49.2˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ S E A 3 38˚ 0.1 38˚ 38˚ 38˚ 38˚ 38˚ 0.08 −0.02 0.01 2 −0.01 −0.02 0.01 Anzali Port 1 00.040.02 37˚ 37˚ 0.040.02 0.02 −0.01 4 0.02 0.02 −0.04 0.01 0.1 0 5 0.25 −0.06 0.25 −0.02 −0.040.04 1 D E F 37.5˚ 37.5˚ 37.5˚ 0.06−0.01 0.25 37.5˚ 37.5˚ 0.5 37.5˚ 6 0.5 0.08−0.02 0.5 7 0.010.250.5 0.04 0.08 0 1 0.08 0.1 2 −0.04 0.08 0.1 Torkaman Port 8 −0.25−0.01 0.25 0.04−0.01 0 2 −0.5 −0.06 −0.02−0.01 0.02 0−0.040 37˚ 37˚ −0.01 0.01 0.04 −0.5−0.02 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 50.4˚ 50.6˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 50.4˚ 50.6˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 50.4˚ 50.6˚ 50.8˚ 9 −1−2 0.01 0 0.250.02 37˚ −0.1 37˚ 37˚ 0 −0.02 37˚ 37˚ −0.1 −0.04 37˚ 5 0.08−1 −0.01 0.1 −0.25 0.1 0.01 0.06 0.06 −1 −0.08 −10.08 −0.01−0.02 −0.25 0.06 0.1−0.010.08−0.06 0.01 −0.25 0 1 2 3 4 5 6 7 8 9 −0.5 −0.04 −0.08 0.1 −0.08 0.01 0.06 0.04 −0.5 0.02 1990 0.1 −0.04−0.1 38˚ 38˚ 38˚ 38˚ 38˚ 38˚ 36.5˚ 36.5˚ 36.5˚ 0.08 36.5˚ 36.5˚ −0.50.25 36.5˚ 1890 36.5˚ 36.5˚ −0.1 0.04 −0.25 −0.06 48.5˚ 49˚ 49.5˚ 50˚ 50.5˚ 51˚ 51.5˚ 52˚ 52.5˚ 48.5˚ 49˚ 49.5˚ 50˚ 50.5˚ 51˚ 51.5˚ 52˚ 52.5˚ 48.5˚ 49˚ 49.5˚ 0.0450˚ 50.5˚ 51˚ 51.5˚ 52˚ 52.5˚ 1608 −0.02 36˚ 36˚ 48.5˚ 51˚ 37.8˚ 37.8˚ 37.8˚ 37.8˚ 37.8˚ 37.8˚ IRAN 49˚ 49.5˚ 50˚ 50.5˚ 958

m cm 37.6˚ 37.6˚ 37.6˚ 37.6˚ 37.6˚ 37.6˚ 47˚ 48˚ 49˚ 54˚ 55˚ 56˚ 50˚ 51˚ 52˚ 53˚ −1000 0 1000 2000 3000 4000 5000 6000 −11.00 −5.00 −2.00 −1.00 −0.50 −0.25 −0.10 −0.08 −0.06 −0.04 −0.02 −0.01 0.00 0.01 0.02 0.04 0.06 0.08 0.10 0.25 0.50 1.00 2.00 5.00 10.00 15.00 20.00 26.00

Reported Tsunamigenic Earthquakes Ambraseys & Melville (2005) 37.4˚ 37.4˚ 37.4˚ 37.4˚ 37.4˚ 37.4˚ USGS M > 6 37.2˚ 37.2˚ 37.2˚ 37.2˚ 37.2˚ 37.2˚ As the initial condition to the equations of hydrodynamics, and in the case of earthquake sources, MOST (e.g., Titov & 0 20 40 0 20 40 0 20 40

2012 Fieldwork Synolakis, 1995) uses the field of static deformations of the epicentral area resulting from the dislocation, as computed 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 50.4˚ 50.6˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 50.4˚ 50.6˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 50.4˚ 50.6˚ 50.8˚ for example through the algorithm of Mansinha and Smylie (1971). We have simulated the tsunami for both single and The 1960 event(?) was the initial subject of our 2012 survey, m composite sources. We can use a linear combination of simulations from the individual subevents due to the low ratio 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 however, it revealed the tsunami of 20 June 1990 which was not of the maximum initial amplitudes to the depth of the water column, which makes the non-linear effect of amplitude 48˚ 49˚ 50˚ 51˚ 52˚ 53˚ 54˚ 55˚ 49.2˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 50.4˚ 50.6˚ Wave Amplitudes Near the Coast formerly recognized. dispersion negligible. 40˚ 40˚ 38˚ 38˚ 6 (SUCCESSFUL) A 5 B 37.8˚ 37.8˚ C 39˚ 39˚ 49˚ 50˚ 51˚ 52˚ 53˚ 54˚ D 39˚ 39˚ CMT Source Composite Source 0.05 3 (A) (E) 4 E Azerbaijan Astara Port F 48˚ 49˚ 50˚ 51˚ 52˚ 53˚ 54˚ 48˚ 49˚ 50˚ 51˚ 52˚ 53˚ 54˚ CMT 37.6˚ 37.6˚ Measurements Astara 29 Witnesses Interviewed Static Composite Source Kiashahr (>2 m) 38˚ 38˚ (B) Perception Level

Kiashahr − Wharf Dynamic Composite Source (F) 3 Limir km Measurement Points (C) (D) Perception Level Havigh 0.04 Kheir−Rood Coastline 37.4˚ Chamkhaleh 0 100 37.4˚ km Amplitude (m) Jafrood (1−2 m) Siahchal

Zibakenar 40˚ 40˚ 40˚ 40˚ 2 Talesh 37˚ 37˚ 38˚ Mazgah 38˚ 2 0 10 20 30 Tonekabon 37.2˚ 37.2˚ 1

Turkmenistan 0.03 Mahmood−Abad Namakabrood Tonekabon Amir−Rood 48˚ 49˚ 50˚ 51˚ 52˚ 53˚ 54˚ 55˚ 49.2˚ 49.4˚ 49.6˚ 49.8˚ 50˚ 50.2˚ 50.4˚ 50.6˚

Shirood 39˚ 39˚ 39˚ 39˚ Naftchal 0 Anzali Latingan 49 49.2 49.4 49.6 49.8 50 50.2 Ruyan slope 0.02 Longitude 38˚ 38˚ 38˚ 38˚ 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 37˚ 37˚ Amplitude (m) 1 Measurements (m) 1990 IRAN 37˚ 37˚ 37˚ 37˚ 0.01 Noshahr Conclusion 49˚ 50˚ 51˚ 52˚ 53˚ 54˚ 48˚ 49˚ 50˚ 51˚ 52˚ 53˚ 54˚ 48˚ 49˚ 50˚ 51˚ 52˚ 53˚ 54˚ 0 0 49 49.2 49.4 49.6 49.8 50 50.2 Our field study failed to identify a legitimate scenario for a definitive inundation in 1960. Rather m Longitude we were able to document a significant tsunami following the major Rudbar earthquake of 20 0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.022 0.024 0.026 0.028 0.030 June 1990, with run-ups reaching 2 m at Kiashahr and most importantly, a concentration of the inundation over a ∼30-km stretch of coastline. These characteristics cannot be modeled using THE EARTHQUAKE SOURCE CANNOT MODEL OUR RESULTS. the Rudbar earthquake dislocation as the source of the tsunami. By contrast, our model (A) of a landslide, presumably triggered by the earthquake, originating around 37.53◦N, 49.92◦E, and extending 20 km in a 340◦ azimuth manages to match the general profile of the reported tsunami Landslide Source along the coast. This suggests that landslides are important contributors to tsunami hazard in 49.8˚ 49.9˚ 50˚ m 37.8˚ 37.8˚ 0 the Caspian Sea.

We have used the method developed by Synolakis et (m) −100 SURVEY RESULTS al. (2002) and Okal & Synolakis (2003) who model 5 blank REFERENCES

4 1.7 0.2 −200

1.4

1.1

0.8 2 Mansinha, L. & Smylie, D., 1971. The displacement fields of inclined faults, Bulletin of the Seismological Society of submarine landslides as hydrodynamic dipoles which 3 37.7˚2.3 37.7˚ 2.6 0.5 −300 blank America 61 are formed as negative (trough) and positive (hump) 2 , (5), 1433–1440.

−400 −→ 1 b 1960 Remains Elusive initial displacements. 0.2 Synolakis, C. E., Bardet, J.-P., Borrero, J. C., Davies, H. L., Okal, E. A., Silver, E. A., Sweet, S., & Tappin, D. R.,

0 −500 b 1960 −→ with a single possible testimony. 2002. The slump origin of the 1998 Papua New Guinea tsunami, Proceedings of the Royal Society of London. Series 37.6˚ 37.6˚ 2 −1 −600 A: Mathematical, Physical and Engineering Sciences, 458(2020), 763–789. b −→ ∼ b − 37.8˚

1990 Runups > 2 m along a 30 km stretch αtx 2 −2 49.7˚ − sech 37.7˚ z = η e (γ y) −1 t t t −2.5 49.8˚ −700

37.6˚ −3 −1.3 Pure and −1.6 Okal, E. A. & Synolakis, C. E., 2003. A theoretical comparison of tsunamis from dislocations and landslides, −→ −1.9 b 1990 of the coast between Kiashahr −0.7 2 37.5˚ −2.2 −α x−l 2 49.9˚

h( ) −4 Applied Geophysics 160 37.4˚ , (10-11), 2177–2188. sech −0.1 −800 −0.4 −→ z = η e (γ y) 50˚ b 1990 and Jafrood. h h h 49.7˚ 37.5˚−0.1 37.5˚

50.1˚ 49.8˚ −900 Titov, V. V. & Synolakis, C. E., 1995. Modeling of breaking and nonbreaking long-wave evolution and runup using b −→ 1990 Fishermen at sea heard noises 37.8˚ 49.9˚ VTCS-2, Journal of Waterway, Port, Coastal, and Ocean Engineering, 121(6), 308–316 37.7˚ −1000 −→ 50˚ b 1990 and felt waves. 37.6˚ 50.1˚ 37.5˚ 0 10 37.4˚ 37.4˚ −1100 37.4˚ b blank 49.8˚ 49.9˚ 50˚ ACKNOWLEDGMENT We wish to thank the Iranian National Institute for Oceanography (INIO) for logistic coordinations and general help during the 2012 fieldwork on the Iranian coastlines of the Caspian Sea.