Fallen Columns from Cathedral at Hippos Sussita Photo of Hippos Sussita

Wechsler and Marco (2017)


Names

Transliterated Name Language Name
Hippos Greek Ἵππος
Antiochia Hippos Greek Αντιοχεία Ἵππος
Hippum Latin
Sussita Hebrew סוסיתא
Sus Hebrew סוס
Sussita Aramaic
Qal‘at al-Ḥuṣn Arabic قلعة الحصن
Introduction

Hippos-Sussita was one of the ten cities of the Decapolis. It declined during Byzantine and Early Arab periods and is believed to have been largely abandoned after it was badly damaged in one of the Sabbatical Year earthquakes. It is situated atop a flat topped ridge which overlooks the Sea of Galilee. Hippos Sussita appears to be subject to a topographic or ridge effect.

Maps. Plans, and Photos
Maps. Plans, and Photos

  • Plan of Hippos-Sussita from biblewalks.com
  • Plan of Hippos-Sussita with excavation areas from Kowalewska and Eisenberg (2021)
  • Plan of the northwest Church from Segal et al (2004)
  • Plan of the northeast Church from Segal et al (2004)
  • Plan of the Forum. Hellenistic compound, and Northwest Church from Segal and Eisenberg (2007)
  • Aerial View of the Cathedral from Kowalewska and Eisenberg (2021)

Chronology
Early 4th century CE earthquake

Segal et al (2014b) excavated an Odeion at Hippos-Sussita from 2008 - 2010. They report that

On the basis of an analysis of the building methods and materials and according to the numismatic and pottery finds, it can be determined to a great degree of certainty that the odeion was erected during the second half of the 1st century CE. It appears that the odeion was in use during the first three centuries of the Common Era. Its condition as revealed during its exposure by the excavators clearly indicates that it was not destroyed. This conclusion is based on the preserved uniform height of the walls, two or three courses, not including the encompassing wall of which six courses have survived. The lack of decorative items that were broken or burnt, the absence of tiles and sooty remains of the ceiling and roof, all testify that the structure was systematically dismantled. It is safe to assume, on the basis of the numismatic and pottery finds, that the dismantling of the structure was carried out during the 4th century CE, apparently before the earthquake of 363 CE. However, we cannot negate the possibility that the odeion was damaged during this earthquake and that a decision was then made not to renovate but rather to dismantle it.
In summary, they did not encounter a destruction layer. While it is possible that the Odeion was dismantled due to damage caused by an earlier earthquake, the excavators did not suggest this.

363 CE earthquake

Wechsler, N., et al. (2018) report the following archeoseismic evidence at Hippos

The destruction of the Roman Basilica built in the center of the city at the end of the 1st century CE is clear evidence for the 363 CE earthquake judging by the archaeological data (Eisenberg, 2016; Segal, 2014a). The latest coins found in-between the fallen architectural fragment and the basilica floor are dated to 362 CE while the floor built above its debris is dated to the 380s CE. It is possible that some of the later, strong, post-abandonment earthquakes caused some additional damage at the site.
Press reports (Science Daily) also indicate the discovery of the skeleton of a woman with a dove-shaped pendant under the tiles of a collapsed roof in an area north of the Basilica which was attributed to the northern Cyril Quake of 363 CE.

mid 8th century CE earthquake

Maps and Plans

  • Plan of Hippos-Sussita from biblewalks.com
  • Plan of the northwest Church from Segal et al (2004)
The Cathedral is the largest of several churches found on the site and is situated south of the Cardo. A fragmentary Greek inscription reveals that it was built in 590 CE (Wechsler et al (2018) citing Latjar, 2014:250-278) and remained in use until the mid 8th century CE (Wechsler et al (2018) citing Segal, 2007). Excavations in the 1950's revealed columns lying on the floor of the cathedral in sub parallel directions (Wechsler et al, 2018). These columns are presumed to have fallen during one of the Sabbatical Year earthquakes.

Segal et al (2004:65) reports that chronological evidence for the one of the Sabbatical Year earthquakes "destroying" Hippos Sussita has been confirmed by the objects found in the sealed contexts at the [northwest] church such as the coins and pottery (including oil lamps): see our Report 2001, 2002 and 2003 respectively. The church referred to is the Northwest Church. This is not the same church Wechsler et al (2018) and others refer to as the Cathedral. It is the Cathedral which contains the fallen columns that Yagoda-Biran and Hatzor (2010) analyzed to estimate a lower limit of paleo-PGA during the earthquake.

Mlynarczyk (2008:256-257) reported the following about archaeoseismic evidence for an earthquake in 749 CE.
The so-called North-West Church, excavated by the Polish team in 2000- 2008,19 yielded a number of invaluable archaeological deposits securely sealed by the debris of an earthquake. There can be no doubt that the earthquake in question was that of January 18th, A.D. 749, since (apart from scores of typical Umayyad-period ceramic vessels) the latest coin, sealed on the floor of the northern aisle, was minted in Tiberias between A.D. 737 and 746.20 Most importantly, the contents of destruction deposits prove that the church was liturgically active till that very moment.21 It was built to the north of the agora (Fig. 1), the central public square (termed “Forum” by the excavators), on the site of an Augustan/Tiberian-period sanctuary,22 not earlier than at the turn of the fifth century (based on the material associated with the stylobate foundation in the atrium)23 or even during the first half of the sixth century. The church builders re-used parts of the cella walls (like the northern wall, in extenso incorporated into the northern wall of the basilica) as well as the stylobate of the eastern portico of the temenos.
Footnotes

19 The institutions, represented by the team members, were the Research Centre for Mediterranean Archaeology (Polish Academy of Sciences), the National Museum in Warsaw and the Institute of Archaeology (University of Warsaw). The work was financially supported by Grant No 1H01 B009 29 of the Ministry of Science and Higher Education (2005-2007).

20 Berman 2001, 38, cat. no. 31. The same earthquake largely destroyed Beisan, cf. Bar-Nathan, Mazor 2007, XIV.

21 Mlynarczyk, Burdajewicz 2003, 31-32; cf. Mlynarczyk 2008a, passim.

22 Mlynarczyk, Burdajewicz 2004, 67-68, fig. 25; Mlynarczyk, Burdajewicz 2005a, 53; Mlynarczyk, Burdajewicz. 2005b, 16.

23 Ibidem, 46.

Seismic Effects
Undated Archaeoseismic Evidence

Plans

  • Plan of Hippos-Sussita from biblewalks.com
Tilted Walls and Structures
Karcz and Kafri (1978) identified tilted walls at the site as shown in Figure 9 and Figure 10 of their article. They noted that at the time their article was written, a reliable date for the tilting was not available.

363 CE earthquake

Seismic Effects include:

mid 8th century CE earthquake

Plans

  • Plan of Hippos-Sussita from biblewalks.com
  • Plan of the Forum. Hellenistic compound, and Northwest Church from Segal and Eisenberg (2007)
Tilted and Displaced Wall in the Area East of the Hellenistic Compound
Segal et al (2019:18) uncovered a wall displaced towards the west in the area east of the Hellenistic Compound (HLC5) which they attributed to one of the mid 8th century CE earthquakes.
The Cathedral
Kowalewska and Eisenberg (2021) noted the following:
The atrium and the southern aisle floors were covered with collapsed building debris, composed mainly of basalt ashlars. Only the lowest ashlar courses of the building’s walls were extant, and in some places even the lowest course was tilted and pushed out of place. The eastern area of the opus sectile floor of the southern aisle was well preserved (F809; Fig. 10).
Fallen Columns in the Cathedral
Fallen Columns from Cathedral at Hippos Sussita Fig. 2.3

Photo of the cathedral with the fallen columns, looking west.

Wechsler et al (2018)


Nine columns of the northern row of the cathedral are oriented N220°E ± 10° and two remaining columns of the southern row are oriented N295°E ± 10° (Wechsler et al, 2018).

Yagoda-Biran and Hatzor (2010) utilized a two-dimensional formulation of the discontinuous deformation analysis (DDA) method (Shi, 1993) to produce a lower bound of 0.2 - 0.4 g for Peak Horizontal Ground Acceleration (PGA) required to topple the columns. The model for their columns was free standing as shown in Figure 2c of their paper and does not include a superstructure such as an architrave or a roof indicating it is likely to produce a conservative (i.e. low) value of minimum PGA required to topple the columns. Input material values for the columns, consisting of red and gray granite possibly imported from Aswan, were
  • E = 40 GPa
  • ν =0.18
  • ρ = 2700 kg/m3
The friction angle (Φ) between column base and pedestal was assumed to be 45°. Optimal contact spring stiffness (2 x 108 N/m) was determined numerically. Simulations were performed for both one and three sinusoidal loading cycles at a variety of frequencies up to 5 Hz. (shown in Figure 3 of their paper). At frequencies of 1.5 Hz. and below, minimum PGA to topple the columns was about 0.2 g for both 1 and 3 loading cycles. Above 1.5 Hz., the single loading cycle simulations were more sensitive to frequency and required a higher PGA to topple the columns. The authors suggested that if only sinusoidal inputs are considered, 3 cycle simulations were more likely be representative of PGA thresholds required to topple the columns. Thus they used the three cycle simulations to produce a range of frequency dependent threshold PGA's required to topple the column that varied from 0.2 g below 1.5 Hz. up to 1 g at 5 Hz..

Recognizing the fairly wide range of threshold PGA's resulting from this analysis, Yagoda-Biran and Hatzor (2010) performed a subsequent set of simulations using strong motion records applied to the centroid of the column and base. The strong motion records came from instrumentally recorded earthquakes thought to be representative of the Dead Sea Transform. The predominant frequencies of these strong motion records varied from 0.45 - 2.2 Hz. and produced threshold PGA's between 0.2 and 0.4 g. Although Yagoda-Biran and Hatzor (2010) did not conclude that their column analysis resulted in an estimated threshold PGA of 0.2 - 0.4 g to topple the columns, it can be reasonably assumed that this is result. However, as mentioned previously, these threshold PGA's are likely underestimated as they modeled free standing columns without a superstructure.

Wechsler et al (2018) commented on modeling the column falls as follows:

The Cathedral is, so far, the only structure that has been at the center of quantitative archaeoseimsic studies. Yagoda-Biran and Hatzor (2010) tried to estimate minimum levels of peak ground acceleration (PGA) during the earthquake ground motion which was necessary to topple the Cathedral columns. However, they used the model of a freestanding column of the same size as the ones found in the Cathedral, but with no capital, architrave or other superstructure. Since 2D models were used and forces were applied to the center of gravity of the columns and pedestals, the reported 0.2 - 0.4 m/s2 PGA threshold at frequencies between 0.2 and 4.4 Hz can only be regarded as a rough estimate and are not necessarily representative for the complete structure of the Cathedral which has a significantly different response to earthquake ground motions than a solitary column. Hinzen (2009) used 3D discrete element models conforming to the size of the toppled columns of the Cathedral and showed that the toppling direction during a realistic earthquake ground motion in three dimensions is a matter of chance. A column that is being rocked by earthquake ground motions is in a nonlinear dynamic system and its behavior tends to be of a chaotic character. Small changes to the initial conditions can have a strong influence on the general dynamic reaction and significantly alter the toppling direction. The same paper shows that the parallel orientation is probably an effect of the superstructure connecting the columns mechanically and not a consequence of the ground motion character. This interpretation is also strongly supported by the fact that the two remaining columns of the southern row rest at angles of ~90° compared with the columns from the northern row, as shown in a 3D laser scan model of the site (Fig. 2.4 ). A similar analysis of the Hippos columns was performed by Hinzen (2010).

Intensity Estimates
363 CE earthquake

Effect Location Notes Intensity
Collapsed Walls Basilica fallen architectural fragment (Wechsler et al, 2018) suggests collapsed walls VIII+
Displaced Walls To the north of the Basilica collapsed roof (Science Daily, 2014) suggests displaced walls VII+
The archeoseismic evidence requires a minimum Intensity of VIII (8) when using the Earthquake Archeological Effects chart of Rodríguez-Pascua et al (2013: 221-224).

mid 8th century CE earthquake

Effect Location Notes Intensity
Displaced Walls east of the Hellenistic Compound (HLC5) Wall displaced towards the west (Segal et al, 2019:18) VII+
Collapsed Walls Northwest Church Segal et al (2004:65) reports that chronological evidence for the one of the Sabbatical Year earthquakes "destroying" Hippos Sussita. Destruction suggests collapsed walls at a minimum. VIII+
Fallen Columns Cathedral Excavations in the 1950's revealed columns lying on the floor of the cathedral in sub parallel directions (Wechsler et al, 2018) VIII+
The archeoseismic evidence requires a minimum Intensity of VIII (8) when using the Earthquake Archeological Effects chart of Rodríguez-Pascua et al (2013: 221-224). Yagoda-Biran and Hatzor (2010) estimated a minimum paleo-PGA of 0.2-0.4 g to overturn the columns found in the Cathedral. This paleo-PGA is a lower bound and therefore an underestimate. Assuming a PGA of 0.4-0.6 g and converting from PGA to Intensity via Wald et al (1999), one arrives at an Intensity of 8 - 8.5 which reduces to ~6.5 - 7.5 when one considers a site effect.

Site Effect
Topographic or Ridge Effect

Topographic or Ridge Effect at Hippos Sussita Fig. 2.5 Simplified north-south trending geological profile through the saddle-like structure of the Sussita hill. On top of the profile, a frequency-dependent seismic amplification is shown which was derived for ten one-dimensional linear elastic models of the subsurface. Abbreviations for the geologic units are given at the bottom of the figure.

Wechsler et al (2018)


Wechsler et al (2018) pointed out that a topographic or ridge effect is likely present Hippos Sussita:
The saddle-like structure of the Sussita hill is prone to topographic amplification of strong ground motion during earthquakes, especially at the hilltop. The focusing effects of seismic waves in similar situations have been reported to lead to significant ground motion amplification (e.g., Massa et al., 2010). In the case of Hippos, the special geometry of the hill is combined with the unusual situation of high impedance material in the form of a basalt flow on top of weaker conglomerates. Figure 2.5 (above) shows a simplified north-south trending profile through the site and the neighboring valleys of Ein-Gev and Sussita. Estimates of ground motion amplification of vertically traveling shear waves from 1D model calculations indicate amplification factors at the hilltop in the range of 8 at frequencies of 2-3 Hz, a frequency range at which constructions such as colonnades show high vulnerability. In any further archaeoseismic studies of the damaged structures in Hippos, the exceptional location of the site and the local conditions must be taken into account.

Calculators
Estimate Magnitude and Intensity with and without a Site Effect

Variable Input Units Notes
g Peak Horizontal Ground Acceleration
km. Distance to earthquake producing fault
unitless Site Effect due to Topographic or Ridge Effect
(set to 1 to assume no site effect)
Variable Output - Site Effect not considered Units Notes
unitless Conversion from PGA to Intensity using Wald et al (1999)
unitless Attenuation relationship of Hough and Avni (2009)
used to calculate Magnitude
Variable Output - Site Effect removed Units Notes
unitless Conversion from PGA to Intensity using Wald et al (1999)
unitless Attenuation relationship of Hough and Avni (2009)
used to calculate Magnitude
  

Magnitude is calculated from Intensity (I) and Fault Distance (R) based on Hough and Avni (2009) who did not specify the type of Magnitude scale they were using.

Site Effect Removal Methodology

  • Figure 13a from Massa et al (2010)
Output with site effect removed assumes that PGA is higher than it would be if there was no site effect. In this situation, Intensity (I) with site effect removed is calculated pre-amplification (i.e. it will be lower). This is because an Intensity estimate with the site effect removed is helpful in producing an Intensity Map that will do a better job of "triangulating" the epicentral area.

Site Effect is based on Equation 2 and Figure 13 a of Massa et al (2010). In their study, they estimated a frequency dependent additional PGA (St in Eqn. 2) which is added by a topographic site effect. The additional topographic site effect PGA varied from ~0.1 g to 0.5 g for dominant frequencies of approximately 1 - 5 Hz.. Higher PGA's were shown to be present for higher frequencies which are more likely to occur when the earthquake producing fault is closer to the site. They also noted that a greater topographic effect was observed when the seismic energy arrived orthogonal (perpendicular in their words) to the ridge. Both of these considerations suggest that a topographic ridge effect should be considered at Hippos Sussita when other evidence suggests that one of the Sea of Galilee faults broke during the earthquake. The additional Site Effect PGA is linearly scaled from 0 - 0.5 g for site effects where amplitude increases from 1x to 10x. It's not the greatest transform to remove site effect from the Intensity estimate but may be useful for crude estimates.

Experimental calculators - Variation of Fourier amplitude spectra - UNDER CONSTRUCTION

Source : Kramer (1996:92-93)

Seismic Moment and Moment Magnitude
Variable Input Units Notes
GPa Shear Modulus
m Displacement
km. Fault width
km. Fault length
Variable Output Units Notes
N-m Seismic Moment
dynes-cm. Seismic Moment
unitless Moment Magnitude
  
Variable Input Units Notes
unitless Radiation Patttern
unitless Free surface effect
km./s Shear Wave velocity of the rock
g/cc Density of the rock
Moment Magntidue
Hz. cutoff frequency - 15 Hz. typical for W N Am.
bars 50 bars typical for W N Am.
Hz. frequency
km. Fault Distance
Variable Output Units Notes
constant
dyne-cm. Seismic Moment
Hz. Corner frequency
Amplitude (UNDER CONSTRUCTION)
  

Notes

Equations
|A(f)| = [C*Mo*(f2/{1-(f/fc)2})*(1/sqrt{1 + (f/fmax)8})]e-{π*f*R/Q(f)*vs}/R         (3.30 - Kramer, 1996:92)

|A(f)| = fourier amplitudes
C = constant
Mo = Seismic Moment (dyne-cm.)
f = frequency (Hz.)
fc = corner frequency (Hz.)
fmax = cutoff frequency (Hz.)
Q(f) = frequency dependent quality factor, inversely proportional to the damping ratio of the rock
π = Pi
R = distance from circular rupture surface
vs = shear wave velocity of the rock

C = RθΦ*F*V / 4*π*ρ*vs3         (3.31 - Kramer, 1996:92)

RθΦ = Radiation Pattern ≈ 0.55
F = Free-surface effect =2
V = √2/2 - accounts for partitioning of energy into two horizontal components
π = Pi
ρ = density of the rock
vs = shear wave velocity of the rock

fc = 4.9 x 106*vs*(Δσ/Mo)1/3         (3.32 - Kramer, 1996:93)

fc = corner frequency (Hz.)
vs = shear wave velocity of the rock (km/sec.)
Δσ = stress drop (bars) - 50 and 100 are typically used for western and eastern North America
Mo = Seismic Moment (dyne-cm.)

Mw = (2/3)*log10Mo-10.7         (2.5 - Kramer, 1996:49)

Mw = Moment Magnitude
Mo = Seismic Moment (dyne-cm.)

fxsolver

Mo = μ*A*D         (2.1 - Kramer, 1996:42)

μ = Shear Modulus (Pa)
A = Area of rupture (m2)
D = displacement (m)

fxsolver

Units
1 Pa = 1 N/m2
1 dyne is the force required to accelerate 1 gram 1 cm/s2
1 N = 100,000 dynes
1 bar = 10^6 dynes/cm2

Photogrammetry
Digital Hippos

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  • link

Notes and Further Reading
References
Wikipedia page for Hippos Sussita