• from Braun (2009:3-4)

Mt Carmel is defined to its east by the NW-NNW Carmel fault, a branch of the Dead Sea Transform System. Denya Cave, located on a spur of this mountain in Haifa, Israel, is a karstic formation, in which broken speleothems, collapsed structures and cracks were observed, and appeared to be evidence of seismically induced damage. This study set out to determine whether broken and deformed cave deposits in Denya Cave are speoleothem seismites from which information regarding the paleo earthquake record of the region during the Quaternary might be extracted.

Following a process of mapping and investigating the cave and excluding non-seismic causes for visible damage, possible samples were examined and extracted from those deposits deemed most likely to have recorded ancient earthquakes. Unconformities in stalagmites, stalactites and flowstone formations were identified as ‘seismic contacts’. Laminae in such broken or deformed speleothems were then sampled for dating as close as possible to their seismic contacts. The ages of these laminae, either pre seismic or post-seismic, define age constraints of damaging events.

A classification method for different types of seismites was added to speleo-seismite analysis in order to determine reliability of results. This was determined according to the type of speleothem, the clarity of the seismic contact as a viable indicator for a seismic event, and the ability to adequately sample material.

Samples were dated utilizing the U-Th (uranium decay) method, a process that is not, however, straightforward as the appearance of detrital matter within samples can alter age determinations. Such adulterations necessitate corrections in order to yield true ages. The ages obtained for Denya Cave seismite samples were corrected for detrital Th using an isochron method based on isochrons. Seismite samples, which were considered to be of the same age when certain criteria were met, were plotted along isochron lines and a single age was determined for them. Criteria for plotting seismite samples along isochron lines are based on stratigraphic considerations in the sample laminae and the amount of detrital matter within the dated sample.

A total of 68 speleothem samples was taken and inspected from Denya Cave, 37 of which were identified as seismites; of them, 32 were processed. Ten seismites are severed stalagmites broken along sub-horizontal plains. Nine seismites of the 32 are severed stalactites of different shapes and sizes. The remaining seismites are flowstone samples in which breaks and depositional unconformities were found; some revealed soda straw speleothems embedded in them.

The isochron calculated ages obtained for groups of speleo-seismite samples indicate that each group records a seismic event. Nine age clusters were determined for speleo seismites from Denya Cave, indicating the ages of seismic events which affected the cave over the last 200ky: 4.8±0.80ka; 10.42±0.69ka; 20.8±3.0ka; 29.1±3.3; 38.0±2.7ka; 57.9±5.2ka; 137±29ka; 147.6±5.4ka and 160±45ka.

A comparison with data available to date from other paleoseismological studies in the region shows that all ages obtained for Denya Cave age clusters can potentially be compared to other ages obtained from other studies in Israel. The comparison indicates that the breaks identified in Denya Cave speleothems, are not random and lends supportive evidence to the assumption that they represent seismic events. Some of the ages obtained from this study might coincide with ages of seismic events dated along the Dead Sea Transform, as well as those along the Carmel Fault. Therefore, future studies are required in order to determine the origin of paleo-earthquakes reported in this study.

• from Kagan (2011:74-76)

Caves create an environment protected from most erosive activity. The calcite and detrital deposits within caves have laminar growth patterns preserving delicate evidence including structural damage from earthquakes. Speleothems can be dated with radiometric methods, making it possible to study the temporal patterns of seismic events [e.g. Kagan et al., 2005; Panno et al., 2009: Plan et al., 2010].

The mechanical relation between earthquakes and the breaking of speleothem structures is not clear. Various aspects of the relation have been investigated in past studies, including investigation of the ground acceleration needed to damage different speleothems, the types of speleothems sensitive to breaking under certain conditions, and predicted modes of failure [e.g. Cadorin et al., 2001; Lacave et al., 2000, 2004; Becker et al., 2006]. Yet speleothems are heterogeneous by nature [Gilli et al., 1999; Lacave et al., 2000] owing to their internal structure, composition, growth rates, and location within a cave. Furthermore, considering site effects and cave depths, shapes and sizes, we are not yet able to precisely predict the effects of earthquakes on speleothems. These considerations make it difficult to evaluate clear intensity values of speleothem damage for intensity scales such as the Environmental Intensity Scale 2007 [ESI07- Reicherter et al., 2009]. Modern observations and detailed investigation immediately following earthquakes need to be carried out for calibration of the past events to quantitative parameters.

Nevertheless, observations of broken speleothems due to modern earthquakes have been documented in caves from around the world [e.g. Gilli et al., 1999; Aydan, 2008; Perez-Lopez et al., 2009]. Dated damaged speleothem samples were reported to have yielded ages of known historical and pre-historic earthquakes in various studies [e.g. Postpischl et al., 1991; Morinaga et al., 1994; Lemeille et al., 1999; Kagan et al., 2005].

Effects of earthquakes on caves and speleothems can come in different forms (Figure 3.3.3). These may include cracks and fissures, severed stalagmites, collapsed and broken speleothems, collapsed ceilings and rockslides, changes in growth axes due to tilting [e.g. Postpischl et al., 1991; Morinaga et al., 1994; Forti, 1998; Gilli et al., 1999; Lemeille et al., 1999]. Another form of earthquake induced damage is the closing or opening of cracks, depending upon their locations in relation to stress fields [Muirwood and King, 1993].



Most paleoseismological and speleoseismological studies seek to date phenomena which occurred almost instantaneously by earthquakes. When a similar age is obtained by a few different speleothem samples from different parts of a cave, it is suggestive that these were not spontaneous separate collapses, but indicative of an earthquake [Kagan et al., 2005; Braun, 2009]. Dating such events can only give an age range due to analytical and geological uncertainties, as in most geological scenarios. These uncertainties can prevent differentiation of closely timed seismic events, but quiescent intervals, as well as periods of clustering, can be identified clearly.

• from Kagan (2011:77)

The Denya neighborhood, hosting the Denya Cave, is within the city of Haifa (Figure 3.3.1) and is situated on a spur sloping down from the summit of Mt. Carmel in a westward direction.

The Denya Cave shows continuous growth of speleothems during the entire Holocene [Bar Matthews et al., pers. comm.]. It is ~ 50m² in area and throughout the cave there is evidence of collapses, as seen in broken speleothems, fallen rocks and a tumbled segment of a cave wall. Cracks in the cave ceilings and walls show oblique displacement of a few centimeters with speleothems growing down from some of the cracks in the ceilings. Thirty-two speleoseismites were sampled and dated. Nine age clusters indicating nine seismic events were determined over the last 200 ky using the isochron method discussed below [Braun, 2009]. In this section we present the Holocene events.

• from Braun (2009:71-72)

Analysis of U-Th ages of speleo-seismites in Denya Cave, using three dimensional isochrons, yielded age clusters that are considered to represent nine seismic events during the last 200kyr BP:

1. A seismic event at ~4.8(±0.8)ka is based on five pre and post seismite samples from around the cave, among them DN-2, which is a type A speleo-seismite.


2. A seismic event at ~10.4(±0.69)ka is based on six pre and post seismite samples from around the cave, where two are type A speleo-seismites (DN-7 and DN-17). This calculated age is considered accurate since it is based on 11 dated samples, of which four DN-7 post-seismite samples are considered to be of the same age and two DN-9 pre-seismite samples that are likewise considered to be of the same age.


3. A seismic event at ~20.8(±3.0)ka is based on eight seismite samples from around the cave. Most of those are pre-seismite samples of type C speleo-seismites. This calculated age is based on 13 dated samples, of which four DN-4 pre-seismite samples are considered to be of the same age and likewise for two DN-6 pre-seismite samples. It is supported by DN-7 pre-seismite sample, which is a type A speleo-seismite.


4. A seismic event at ~29.1(±3.3)ka is based on a well constrained type A speleo-seismite (DN-48 pre and post samples) and is corroborated by four other pre- and post-seismite samples from around the cave.


5. A seismic event at ~38(±2.7)ka is based on a well constrained type A speleo-seismite (DN-44 pre and post dated samples) and is corroborated by six other post- and pre-seismite samples from around the cave.


6. A seismic event after ~57.9(±5.2)ka is based only on pre-seismite samples, usually of type C. Its isochron plot is scattered and gives a high error on the calculated age. It is still considered an indicator for a seismic event, which occurred after that time, since it is based on six different speleo-seismites from around the cave.


7. A seismic event at ~137(±29)ka is based on five pre and post seismite samples from around the cave. Most of those samples are from type C speleo-seismites. The age calculation is based on sample ages with large errors and is therefore less reliable.


8. A seismic event at ~147.6(±5.4)ka is based on four type A pre and post seismite dated samples from around the cave. The age calculation yielded a minimal scatter isochron plot.


9. A seismic event at ~160(±45)ka is based on five pre and post seismite dated samples from around the cave. Three of those samples are type A speleo-seismites. The age calculation is based on sample ages with large errors and is therefore less reliable.

• from Braun (2009:72-74)

One way to verify if the accuracy of ages obtained are valid as seismites is to correlate them to known, well established ages of seismic events (e.g. Kagan et al., 2005). As noted above, data on paleoseismic activity on the CF are scarce and often not very accurate and there is no clear evidence of historically known earthquakes. Nevertheless, some information is available (Table 8 and Fig. 40) Since Mt. Carmel is at a similar distance from the DST as Soreq Cave is (Kagan et al, 2005), an initial comparison of the ages obtained from Denya Cave seismites to ages obtained from DST paleoseismic studies, is made (Table 8 and Fig. 40). The comparison showed some matching ages. If such is the case, it is not clear which of those two fault systems caused damage to speleothems analyzed from Denya Cave.

The sample age cluster at ca. 5ka from Denya Cave may correlate well to the seismic event which caused structural damage to the EB I temple at Megiddo (Marco et al., 2006) as well as to six damaged speleothems dated to that approximate time (4.9-5.7ka or older) at Soreq cave in the Judean Hills (Kagan, 2002).

A seismic event at ca. 10ka is very clearly documented in Denya Cave speleo seismites but is too old to be observed in Megiddo, which has no archeological evidence from that period. That age might also be too young to be noted in paleoseismic trenches, which were dug along the CF in the Kishon Valley, since most of the upper layers in that area may have been disturbed by human activity (Zilberman et al., 2006). This event was not recorded at all in Soreq Cave as well. It might have been recorded in two paleoseismic trenches in the area of Ein-Gev, along the northern segment of the DST, which were dated to ca. 11ka (Amit et al., 2009).

The seismic event recorded in Denya Cave speleothems at ca. 21ka might be supported by the age of the upper part of the shutter ridge dated by Zilberman et al. (2006) to 24.5±2.5ka, which was followed by an incision of the stream channel and assumed to be indicative of fault movement.

A seismic event at ca. 29ka, obtained from Denya Cave speleothems, might be supported by the ages obtained for a layer in a paleoseismic trench along the Nesher fault, which indicates a termination of a 50ka long subsidence, dated to 27±1ka (Zilberman et al., 2006).

The well constrained age of ca. 38ka for a seismic event, which affected Denya Cave, could probably be supported by three different paleoseismic findings. The first, an event reported by Kagan et al. (2007) at ~39±1 ka, which has left evidence of brecciated marls at four Lake Lisan sites along the Dead Sea basin as well as five well-constrained collapses in different areas of the Soreq cave. Another one is a stratigraphic step in a paleoseismic trench along the CF, which was dated to 32±4.4ka, and indicated that the faulting occurred before ca. 35ka (Gluck, 2002). And the last is the dated layers to ca. 37ka in two paleoseismic trenches in Ein-Gev (Amit et al., 2009).

The age cluster of ca. 58ka is based on pre-seismic event samples from Denya Cave, which indicates that a seismic event occurred sometime after. This age might possibly be supported by three collapses dated in Soreq cave speleo-seismites, and Lake Lisan brecciated marls at three sites, which all yielded an age of 52±2.

The sample age cluster of ca. 137ka may possibly be supported by the age obtained for a post collapse growth on a ceiling block, dated in Har-Tuv cave to be younger than 135ka (Kagan, 2002).

The age cluster of ca. 148ka was obtained from only four dated samples. Nevertheless, it is corroborated by dated speleothem samples from Har-Tuv and Soreq caves, which yielded ages between 144 and 155ka (Kagan, 2002). It might also be corroborated by the age of material from the base of the shutter ridge studied by Zilberman et al. (2006), which was dated to 146±20ka. It should be noted that the error margin for that age is much larger than that of the age cluster from Denya Cave (147.6±5.4).

Although the age cluster that was determined by Denya Cave seismite samples at 160±45 has a large error, it might nevertheless be compared to the age, reported by Zilberman et al. (2006), for a layer in a paleoseismic trench, which indicated subsidence of a small basin south of the main fault, and was dated to 176±30ka. A collapsed pillar in Soreq cave yielded a post-seismic age of ca. 163ka, and might also be compared to this age cluster.

Ages obtained for Denya Cave age clusters can potentially be compared to other ages from paleoseismological findings in Israel. The likelihood that this correlation is random can be estimated by randomly picking age ranges from the interval of the entire record, namely 0-206 ka. Each of the Denya Cave dated events cumulatively occupy a finite time range, and the chance for it to correlate at random with the time occupied by other records is given by the ratio between the latter (total=149.9ky) and the range of dated time (204.1ky). Each separate event dated by Denya Cave speleo-seismites has a ~70% chance of randomly correlating to one of the other ages dated by different studies. For all nine dated events to correlate, this figure needs to be raised by the power of nine events recorded in Denya Cave (i.e. {[149.9/204.1]^9}*100), giving a ~6% chance. Those numbers consider the errors on the given ages, which are higher for most of the ages older than 100ka. The same estimation was done for the likelihood that the six age clusters, which yielded younger ages than 100ka, dated from Denya Cave speleo-seismites could all randomly be correlated to other dated seismic events. It was found that for there is a ~3% chance of that to happen (i.e. {[49.9(time occupied by other dated events)/88.1(the range of dated events)]^6}*100).

These results further enforce that age clusters obtained from Denya Cave speleo seismites are not random, and are indicators of seismic events. This comparison also indicates that there is a possibility that some of those events might have originated from the DST and not the CF.