What is an Organic Trauma?

This is a very interesting topic and I consider it important to develop at this time where all the inhabitants of the metropolitan area of ​​Mexico City, Morelos state, Puebla, Oaxaca, Chiapas and the entire Mexican Republic as well as the rest of the world who in one way or another they have experienced difficult situations due to the modifications that occur in the natural environment, such as hurricanes, earthquakes, floods, landslides, volcano eruptions, etc. As well as other situations that modify the social environment such as wars, attacks, etc. What do we define as an Organic trauma? According to Peter Levine, He considers that "trauma the potential to be one of the most significant forces in evolution and psychological, social and spiritual awakening" He considers that the way trauma is dealt with (as individuals, communities and societies) will be seen the great influence on the quality of our life. We can even understand how the impact affects the fact of our own survival in our species. Traditionally, organic trauma has been considered as a psychological and medical disorder of the mind. Peter Levine reflects on the fact that both modern medicine and psychology begin to manifest the relationships between people's minds and bodies, they have not yet integrated the deep relationship that is established between these elements and the importance of seeing them as functional unit for the healing process of organic trauma. If we learn to see this inseparable functional unit between the body and the mind of the person, over time, we will observe how the practical and philosophical underpinning of most of the traditional healing systems around the world is generated, where it is generated an absence of this functional unit for the restoration of the capacities that the person can live. For Moshe Feldenkrais this functional unit not only consisted in the close and inseparable relationship that the person lives from their movements, sensations, emotions and thoughts, in an environment (social, natural, work, political, family, etc.) in relation to the forces of nature (gravity, electromagnetism, and the two nuclear ones), which is in constant interaction, thus determining the way each individual acts.

Within the process of organic trauma, on this occasion I will observe the point of view of the experience of an earthquake, I will take as an example what happened on September 19, 2017, in Mexico City and for this I will include an article developed by researchers from UNAM where they explain what happened from the point of view of engineering and seismology. Because it is important to understand this point of view, because in this article we are taught to understand how a natural environment behaves in an event of this nature and it is important as part of this functional unit that we are by acting to know and understand how these events develop in which we live, which allows us to orient ourselves in our lives. UNAM Seismology and Engineering Groups Informative note What happened on September 19, 2017 in Mexico? We wonder a lot if the magnitude 7.1 earthquake was stronger in Mexico City than the magnitude 8.1 earthquake of 1985. Just because of the enormous difference in magnitude of the two events, one might assume that it was not. This makes sense, since the 1985 earthquake released 32 times more seismic energy than the one on September 19, 2017. However, we all know that, in 1985, the epicenter was very far away and under the coasts of the state of Michoacán, a more than 400 km from the capital, while 7.1 occurred just 120 km south of the city. As they propagate, seismic waves quickly attenuate. Therefore, despite the fact that the rupture that generated the seismic waves last Tuesday is much smaller than that of 1985, the shocks in Mexico City were so violent. Next, we will see why.

Where and why did the earthquake occur? The rupture of the earthquake of September 19, 2017 occurred within the Cocos oceanic plate (i.e. intraplate earthquake), below the continent, at a depth of 57 km (Figure 1). While this type of earthquake is not the most common in Mexico, it is by no means extraordinary. Figure 1 shows the epicenters and depths of some similar earthquakes, including the one last Tuesday. These ruptures occur at depths greater than typical subduction earthquakes such as the 1985 earthquake, which takes place under the Mexican Pacific coast on the interface of contact between the Cocos and North American tectonic plates (red line, Figure 1). Inter-plate earthquakes, of intermediate depth, are produced by extensive stresses along the Cocos plate. The geological faults associated with these earthquakes are known as "normal faults". It should be mentioned that studies carried out for intraplate earthquakes in Mexico show that, per year, the probability that the intensity of the shakes in Mexico City due to this type of earthquake is large is very similar to that of typical subduction earthquakes. , like the one from 1985, among others. This implies that the seismic danger in the capital, associated with intraplate earthquakes (such as those of September 7 and 19, 2017), is as great as that of the most common earthquakes that occur under the Mexican Pacific coast. Why so much damage? Thanks to the vast network of accelerometers and seismometers that recorded both earthquakes in Mexico City, and the efforts of many Mexican seismologists and engineers, today we have a better understanding of what happened. One of the Ingredients that civil engineers use to calculate the structures of the CDMX buildings is the maximum acceleration (Amax) of the ground produced by seismic waves. In 1985, the Amax in Ciudad Universitaria (CU), which is on firm ground (Figure 2), was 30 gal (1 gal = 1 cm / s2), while the Amax on September 19, 2017 was 57 gal . In other words, the soil in the area near CU experienced a shock twice as much as in 1985.

Figure 1: Locations of the 7.1 magnitude earthquake of September 19, 2017 (red color) and some others of the same type in the region. However, we all know that much of Mexico City is built on soft sediments from the ancient lakes that existed in the valley. These sediments cause an enormous amplification of seismic waves in Mexico City, which is probably the largest reported in the world.

Figure 2: Thickness of the sedimentary basin where a large part of Mexico City is located. Note the location of the September 19 earthquake in the box at the top left. The blue dots indicate the sites of two seismic stations that recorded the 1985 and 2017 earthquakes. The region between the blue and red outlines represents the transition zone between firm ground and soft ground. To give a tangible idea, the amplitude of seismic waves with periods close to 2 seconds in the lake zone (or soft zone) (eg colonias Roma, Condesa, Centro and Doctores) can be 50 times greater than in a site of firm ground of Mexico City. However, as the waves are also amplified on the firm ground of the periphery, with respect to distant places in Mexico City, the amplitude in the lake area can be 300 to 500 times greater. At some sites in the lake area, the maximum ground accelerations produced by the magnitude 7.1 earthquake were lower than those recorded in 1985. For example, in the Secretariat of Communications and Transportation (SCT, Figure 2), which is located in that area, Amax in 1985 was 160 gallons, while on September 19 it was 91 gallons. At other sites in the lake zone, ground accelerations during the recent earthquake were most likely greater than those recorded in 1985. This is a complex and highly variable pattern of movement in space.

Figure 3: Location of serious damage and collapse during the earthquake of September 19, 2017 (red dots). The background map contains information on the natural period of the soil (color gradient), which is a characteristic that determines the amplification potential of the city's soft soil. The gray-toned area represents the 0.5 to 1.0 second periods, also known as the transition zone. (Source: ERN Ingenieros Consultores, ERNTérate, “Note of interest regarding the earthquake of September 19, 2017”, published on September 23, 2017. A detailed analysis of the movement of the soil produced by both earthquakes in Mexico City reveals interesting things. In the same way that it happens with the sound emitted by a guitar string, earthquakes are made up of waves with different periods of oscillation. The recorded seismograms show that the amplitude of seismic waves with periods of oscillation less than 2 seconds was much greater in 2017 than in 1985 (on average about 5 times), roughly, in the entire city. Surprisingly, the opposite happens for waves with periods longer than 2 seconds, whose amplitude was much greater in 1985 (up to 10 times greater). As we will see below, this has strong implications for the type of damage observed during both earthquakes. In summary, the ground movements due to the magnitude 7.1 earthquake were very violent and, in a way, comparable to those of 1985 despite being caused by a much smaller rupture (geological fault) that, however, occurred a lot closer to the City.

And the buildings, what did they feel? For buildings, the situation is not so simple. Maximum ground acceleration (Amax) is not necessarily what puts your stability at risk. On the contrary, being structures of different dimensions (heights), their vulnerability is very varied. Waves with a longer period of oscillation threaten taller structures. Conversely, waves with shorter periods threaten lower structures. To identify which structures may have been affected by the 2017 earthquake, engineers and seismologists calculate what they call "spectral accelerations" from the recorded seismograms. These values ​​give us an idea of ​​the accelerations that buildings with different heights could experience on their roofs. Spectral accelerations in CU (firm ground) indicate that the 1-12 story buildings near the seismic station experienced an average acceleration of 119 gal, which is approximately 2 times greater than that observed in 1985 (Figure 4a). In contrast, estimates in SCT (soft ground) show that small buildings of this type, close to the station, experienced an average acceleration of 188 gal, very similar to those of 1985 (Figure 4b). On the other hand, taller buildings, between 12 and 20 stories, experienced an average acceleration in CU of 60 gallons, which is 30% less than that of 1985, which was 85 gallons (Figure 4a). The clearest difference between the two earthquakes occurred on soft ground for buildings with more than 15 stories. Figure 4b clearly shows how, in 1985, buildings of this type near SCT experienced accelerations of 1.5 to 4.9 times larger than those observed on September 19, 2017. In 1985, some of these large structures experienced accelerations of up to 760 gal. For reference, the acceleration of Earth's gravity (i.e. that of a body in free fall) is 981 gal.

As we will see below, the SCT station is not in the area with the greatest damage, which is further west (towards the Roma and Condesa colonies), mainly in the transition zone of the sedimentary basin. An analysis similar to that of Figure 4 from records in these colonies will allow estimating what types of buildings were the most threatened. In that area, we expect accelerations greater than those of SCT for buildings with 4 to 10 floors.

Figure 4: Accelerations experienced on the roofs of buildings with different heights at sites CU (a, firm ground) and SCT (b, soft ground) (see Figure 2) for the earthquakes of September 19, 1985 (red) and 2017 ( blue). 1 gal = 1 cm / s2. The reported accelerations correspond to the geometric average of both horizontal components of the movement. UNAM engineers and seismologists, thanks to multiple investigations based on thousands of seismic records in Mexico City and the development of sophisticated tools have been able to map, throughout the urban area, acceleration values ​​experienced on September 19 for different types of structures. These tools were developed at the UNAM Engineering Institute and operate automatically in real time. With them, intensity maps are generated throughout the city a few minutes after the earthquake, which are useful to quickly identify potentially damaging areas. Figure 5 clearly illustrates this for the earthquake of September 19, 2017. There it can be seen that there is a clear correlation between the damage that occurred (i.e. buildings collapsed or heavily damaged) and the areas where the greatest accelerations occurred. spectral. Consistent with what was explained in the previous paragraph, the magnitude 7.1 earthquake damaged, for the most part, relatively small structures, between 4 and 7 stories, along a strip with a north-south orientation within the transition zone ( between the areas of firm and soft ground) to the west of the lake area (Figures 3 and 4). In contrast, the structures damaged in 1985 were mostly larger, with heights between 7 and 14 stories.

Figure 5: Map of spectral accelerations for periods of 1 second, corresponding to the response of structures from 7 to 10 floors. The black triangles show the locations of collapsed or heavily damaged buildings. Why was the damage concentrated in certain areas of the city? The violence of the movement of the soil in Mexico City depends mainly on the type of soil where we are. As already mentioned, a large part of the city is settled on soft soil, on lake sediments (red outline in Figure 1). Figure 5 shows the estimated acceleration on the roofs of buildings with 7 to 10 floors (i.e. with resonance periods close to 1 second) caused by the earthquake of September 19, 2017. It should be noted that this map was generated in the form automatic, almost in real time, by the Engineering Institute of the UNAM, for which it was made public a few minutes after the earthquake. As already mentioned, there is a clear correlation between the red band of maximum acceleration to the west of the basin and the location of the collapsed or heavily damaged buildings. The correlation between the large acceleration values ​​(red band) and the geometry (thickness) of the lake sediments is also surprising (Figures 2 and 3). Most of the damage is found to the west of the sedimentary basin, on the transition zone and part of the soft soil, very close to its western limit. There, the sediments are 10 to 30 m thick. The interaction and amplification of the seismic waves with this region of the sedimentary basin caused the damages.

In addition to the amplification of the waves, the duration of the movement of the soil is also much greater within the soft sediments. Recent studies show that the longest expected durations for oscillation periods of less than 2 seconds coincide with the zone of greatest destruction for the 7.1 magnitude earthquake of September 19, 2017. For example, the duration of the intense phase of the movement in CU it was 36 seconds, while in SCT, it was 1 minute. For this reason, both the violence of the shocks and their duration in the transition zone and lake are the causes of destruction.

Was the damage due to deficiencies in the building code?

To date, we have no indications that the design forces (ie the structural resistance criteria) currently in force in the construction regulations of Mexico City have been exceeded during the earthquake of September 19, 2017. Therefore, the Buildings built in recent years should not have been damaged. However, in the case of common structures, the city's Building Regulations do not require that older buildings be reinforced to withstand the forces specified in the standards issued after their date of construction. It is possible, then, that in the case of old buildings, the design forces with which they were projected have been exceeded.

Regardless of the foregoing, it is known that there is a serious problem due to lack of compliance with the standards specified in the current construction regulations, documented in research projects carried out at UNAM. Consequently, the observed damages are better explained by the lack of observance of the regulations, rather than by possible deficiencies in the current Construction Regulations.

Do we expect an earthquake of greater intensity in Mexico City? It is very probable. Under the coasts of the state of Guerrero, for example, there is a seismic gap (ie segment where a significant earthquake has not occurred in more than 60 years) of 250 km in length where an earthquake of magnitude greater than 8 could occur. It is located about 300 km from Mexico City. In other words, approximately 150 km closer than the epicentral zone of the 1985 earthquake. Estimates made by seismologists from UNAM suggest that, if this earthquake Should it occur in the future, the soft ground accelerations in Mexico City could be, under certain conditions, greater than those of the recent earthquake of magnitude 7.1, and 2 to 3 times greater than those of 1985 in particular for buildings of more than 10 floors. The duration of ground movement would be longer than those experienced in 2017 (around 3 minutes in its intense phase).

Nota preparada por:

Dr. Víctor Manuel Cruz Atienza Departamento de Sismología Instituto de Geofísica, UNAM

Dr. Shri Krishna Singh Sismólogo y Profesor Emérito Instituto de Geofísica, UNAM

Dr. Mario Ordaz Schroeder Coordinación de Ingeniería Sismológica Instituto de Ingeniería, UNAM

La información utilizada para elaborar esta nota resulta del esfuerzo de muchos investigadores y técnicos académicos de los institutos de Geofísica e Ingeniería de la UNAM.