Download Figure 8-21 Distribution of Lava Flow for the Model

Figure 8-21 Distribution of Lava Flow for the Model
2)
Pyroclastic Flow
The energy cone model was used for the simulation.
The angle of inclination of Energy Line, φ, from the summit was 5.3 degrees from
the results of the field identification. Five degrees was adopted for the simulation.
b. The eruption column altitude was set to be 10,000 meter or lower, as stromboian activities or subplinian activities are assumed as an eruption style. The eruption
column is assumed the common item for the tephra fall and pyroclastic flow.
c. An occurrence of pyroclastic flow is assumed to be at the central point of the summit where the degree of hazard is the highest from pyroclastic flow.
d. Calibration is not necessary, since the area of influence is assumed from Energy
Line based on the results from field identification.
Tephra fall (ash fall)
3)
a.
The simulation is conducted based on the model of T. Suzuki (1983).
a.
The 1995 eruption of Cerro Negro is used as the model. Calibration is based on
the distribution of tephra fall during the 1995 eruption of Cerro Negro.
b. The total amount of erupted materials and distribution of particle sizes are incorporated based on the analysis of reference materials of the 1995 eruption of Cerro Negro.
c. As for upper-layer metrological data, there was no data observed in Leon. The
data in Managua provided form the counterpart is statistically processed and used.
d. An eruption at the summit of the mountain which has the effects in large areas was
assumed.
e. The eruption column altitude is set to be 10,000 meter or lower, as stromboian activities or subplinian activities are assumed as an eruption style.
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Table 8-6
Average Wind Velocity in the Altitude of 10000m or Less
Altitude
0 - 100
100 - 500
500 - 800
800 - 1500
1500 - 3000
3000 - 6000
6000 - 7500
7500 - 10000
10000 -
August
1.0
5.0
10.0
12.0
12.0
10.0
5.0
5.0
5.0
October
1.0
5.0
5.0
6.0
4.0
4.0
4.0
4.0
4.0
April
1.0
5.0
10.0
10.0
5.0
5.0
5.0
5.0
5.0
Unit: m/s
4)
Volcanic Bomb
The simulation was conducted based on the model of Iguchi and Kamo (1984).
a. An eruption possible areas were set as possible eruption that affects large areas.
b. The dimension of the target volcanic bomb is 10cm or large that is not to be affected
by the convection current in eruption column.
c. In the ballistic calculation, the main axis is assumed to be inclined in advance for
hazard map preparation at the time of a volcanic explosion (See Figure 8-22).
That is, the main axis at the time of explosion is not set perpendicular, but it should
have the gradient of 39 degrees from earth surface. When this is the case, the distance of ballistic travel distance becomes 1.69 times longer than that of the perpendicular case. For the preparation of hazard mapping, the main axis is assumed to
be inclined to all the directions.
d. Since there is no source material, calibration is not conducted.
Vmax axis of explosion
39 degrees
Figure 8-22 Diagram of Explosion Axis (Longest Distance Case)
5)
Lahar
The simulation is conducted in accordance with the hazard assessment by the USGS for
the Volcán Telica (R.M. Iverson, et al., 1998).
a.
Generation of lahar is assumed to be in the following order: collapse of a volcanic
edifice; debris mass movement; debris avalanche; erosion and mobilization of the
mass accompanied with movement; and lahar.
b. The area of influence is set according to a rule of thumb (R. M. Iverson, et al.,
1998).
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c.
d.
e.
(4)
From the past data and geomorphologic conditions, we assumed that the starting
point of lahar has, in general, a slope with 8 to 10 degrees at the ravine floor.
The maximum scale of lahar is set at 3×106 m from the experience of the lahar at
Volcán Casita caused by Hurricane Mitch in 1998. In the simulation, along with
the maximum scale, smaller scales of 1×106m , 0.3×106m3, and 0.1×106m3 are
examined.
Since there is no data or information, calibration is not conducted.
Development of Simulation Software
The simulation software was developed based on the existing simulation software and
the existing simulation program already available. Software was designed in a way to
transfer the results of calculation to the GIS software.
1)
Precondition
Target volcanic phenomenon: lava flow, pyroclastic flow, tephra fall (volcanic ash),
volcanic bomb, lahar
Fundamental requirement: Since there are various cases: lava flow and tephra fall take
time; volcanic bomb requires detailed topographic into consideration, the software needs
to have independent calculation functions for each hazard type and to calculate individually instead of one integrated system.
Geographical accuracy: Topographic-map accuracy of 1/50,000
2)
Execution environment
Lava flow
(a)
Geographical-feature model: 100 m mesh altitude
Computation time: middle to long (30 minutes - about 6 hours)
Program source: FORTRAN
System creation: Visual FORTRAN
Dispatching: Start an executable file from Windows.
Output: ESRI grid ASC file
Pyroclastic flow
(b)
Geographical-feature model: 100 m mesh altitude
Computation time: Short to Medium (several minutes - about 30 minutes)
Program source: FORTRAN
System creation: Visual FORTRAN
Dispatching: Start an executable file from Windows.
Output: ESRI grid ASC file
Volcanic Bomb
(c)
Topographic model: ESRI TIN or 10 m mesh altitude
Computation time: Inside (about 30 minutes)
Program source: Avenue or FORTRAN
System creation: ArcView or Visual FORTRAN
Dispatching: Perform a script from ArcView.
Windows.
Output: shape file or ESRI grid ASC file
Tephra fall
(d)
Geographical feature model: (nor required)
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Or an executable file is started from
Computation time: It is greatly dependent on the number of particle diameter classification, and the number of altitude classification. Generally it is long (several hours
to 10 hour).
Program source: FORTRAN
System creation: Visual FORTRAN
Dispatching: Start an executable file from Windows.
Output: ESRI grid ASC file
Lahar
(e)
Geographical-feature model: 100 m mesh altitude
Computation time: Medium (about 30 minutes)
Program source: FORTRAN
System creation: Visual FORTRAN
Dispatching: Start an executable file from Windows.
Output: ESRI grid ASC file
(5)
System Requirement
The system requirement for the implementation of simulations is described as follows.
In the system, Visual Fortran and Visual C++.Net, one license each, are installed to a PC
in the Department of Geography by the Study Team.
1)
Visual FORTRAN
Software vender: Intel
Product Name: Windows Version Intel Corp.
sional edition
Visual Fortran Compiler
8.1 profes-
Web Site: http://www.xlsoft.com/jp/products/intel/compilers/iftnwin.html
2)
Visual C++.Net
Software vendor: MicroSoft
Product Name: Visual C++.Net 2002
Web Site: http://msdn.microsoft.com/
3)
Arc View
Software vender: ESRI
Product name: ArcView, 3D Analyst
HP: http://www.esrij.com/products/arcview3/index.shtml
(6)
Default Values of the System
The default values of the system were set. The values were the parameters recommended for hazard simulation in the Study area and recommended by theoretical papers,
which were the bases of the system. As for actual operation, 2-2 Volcano in Manual 2 ,
Hazard Mapping. shall be referred. The default values are set for the areas of the
Telica-El Hoyo volcanic complex. For other volcano or other rock types, new parameters need to be set. Figure 8-23 is a sample of default values of the tephra fall
case.
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Figure 8-23 Sample of the Default Value of Tephra Fall Simulation
(7)
Implementation of Simulation
Examples of simulation results are shown in figure from Figure 8-24 to Figure 8-28.
Figure 8-24 is the case of Volcán El Hoyo where a large scale lava flow took place.
The direction of lava flow changes as landform changes near the volcano and other fine
landforms that restrict flow directions and alter the courses of the flows.
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Figure 8-24 Example of Simulation Result on Large Scale Lava Flow from Volcán El Hoyo
The difference in color shows thickness of lava flows.
Figure 8-25 Example of Simulation of Pyroclastic from the Summit of the Volcán El Hoyo and
Energy Line Angle
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Figure 8-26 Example of Simulation on Tephra fall from the Summit of the Volcán Telica
（Top: The same condition as in Cerro Negro 1995. Middle: The eruption column is
twice as high as in the case of the Cerro Negro 1995 eruption; other conditions are the
same. Bottom: The amount of pyroclastic objects are twice as large as the case in the
Cerro Negro 1995 eruption; other conditions are the same.)
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Figure 8-27 Example of Lahar Calculation from Volcán Telica
The difference in colors show the difference in the amount of flooded debris. The pink
color shows the maximum amount of 3x106m3, and the blue color shows the minimum
of 0.1x106m3.
Figure 8-28 Example of Computation in an Case of Ejecta Discharge from the North of the
Summit
The difference in colors show the travel distances by diameters of ejecta. The red is
the case of 30 cm; the yellow is 50 cm; and the light blue is 1 m with an initial velocity
of 150 m/s.
(8)
1)
Hazard Mapping
Existing Volcano Hazard Maps
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In Nicaragua, the following hazard maps are already created in cooperation with the
Mexico Local Autonomy College, etc. The maps have been distributed to municipalities and the Civil Defense and other related institutions.
•
•
•
•
•
•
Volcán Concepción (Volcanic Bomb, Lava Flow)
Volcán Concepción (Pyroclastic Flow, Tephra fall)
Volcán Concepción (Lahar, Collapse of Volcani Edifice)
Volcán Masaya (Volcanic Bomb)
Volcán Masaya (Three types of ash fall by month)
The Centeral - Northern Regional Volcanic Hazard Maps (Lava Flow, Lahar, Collapse of volcanic edifice, pyroclastic flow)
Among the hazard maps listed the hazard maps for Volcán Concepción and Volcán Masaya are prepared in A0 size paper format. The contents seem to be targeted to academics; they are highly specialized for professionals. The existing hazard maps are too
technical for the staffs in the municipal governments and the Civil Defense.
2)
Map Users
How hazard maps are to be prepared depends on the target users. For example, wording, technical terms, uses of illustrations, notations of hazards and other factors can be
different. Also, how well the users can read maps is a factor, which affects how the
hazard maps are to be prepared. Home use or targeted to persons in charge of disaster
prevention is another factor to be considered. If the maps were to be used in the Civil
Defense, a large format which could be put on a wall would be appropriate; for the general home uses, it would be appropriate to have a smaller format.
The hazard maps prepared during the Study, after discussions with the counterpart, are
targeted to the staffs in local governments and the Civil Defense; therefore, literacy has
not been taken into consideration. Since the hazard maps, such as in the maps for
Volcán Concepcion created by INETER are targeted for professional, the hazard maps
for the Study are designed for general users.
3)
Scale of Volcanic Activities and Return Period
It is generally difficult to assume a scale of volcanic activities and return periods from
statistical processing even when sufficient geological researches have been conducted.
This is because almost all the stratums cannot be seen because of the structure in a case
of the stratovolcano characterized in many parts of Nicaragua.
For the reasons, when a hazard map is prepared, users' and decision makers' subjective
purposes are taken into consideration. Alternatively, eruptions of similar volcano are
studied and assumptions need to be set. Even using a historical record, one might not
be able to assume the maximum scale to be a volcanic activity once in one thousand
years.
In general, following cases are considered to determine assumptions on a scale of volcanic activity. Which case to be employed needs to be determined by examining past
records or social conditions one by one.
(1) Gigantic or largest scale in historical records
(2) Most frequent scale in historical records
(3) Gigantic or largest scale in limited geological records
(4) Most frequency scale in limited geological records
(5) Scale of the specific event
(6) Theoretically inferred scale
(7) Designed Scale
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When treating many volcanic phenomena in a volcanic hazard map, it is also unavoidable to have different assumption standards for each volcanic phenomenon; the data
need to be available to determine the same standard level. For the Telica-El Hoyo
volcanic Complex, existing reference materials, results from field identification and
others were used to set assumptions on the scales of eruption.
Lava flow: The maximum scale (apparent volume) among lava flows whose distribution can be identified on the surface at present. It was reported that the maximum lava
flow of Volcán Telica had taken place in 1570. The eruption type like shield basalt or
plateau basalt is not assumed.
Tephra fall: The actual record of the scale (eruption column height, apparent descent
alimentation) in the 1995 eruption of Cerro Negro was the basis of the assumption. A
larger version was also considered.
Pyroclastic flow:
It is based on the field identification.
Although the pyroclastic flow deposit is not confirmed by field identification in Volcán
Telica, the same conditions (energy line angle) were considered as in Volcán El Hoyo.
Volcanic bomb:
periences.
The maximum initial velocity was set at a time of eruption from ex-
Basic Structure
4)
Following subjects are the constitutions of planning the basic structure of the hazard
maps:
(1) The target area of the hazard map for the Telica-El Hoyo volcanic complex is about
1,300 km2;
(2) The hazard map includes five phenomena: lava flow, tephra fall, volcanic bomb;
pyroclastic flow and lahar;
(3) Among the five types, ash fall has larger impact areas; therefore, the scale of background map is different from other four types.
(4) The target users are the staff in the Civil Defense or the staff with similar background.
The smallest scale of the background topographic map is 1/100,000. With the scale,
the target area can be shown with an A2 size paper. When explanation is included, an
A1 size paper would enable to include all the information. However, in the case of ash
fall in Volcán Telica and Volcán El Hoyo, the size becomes an A1 size. With other
information included, an A0 size become the size of the hazard map. At most, six hazard maps, or when overlaid, about three hazard maps need to be prepared.
When the condition (3) is considered, it would be better to use a large format for easier
interpretation to be posted on the wall all the time. In the past, the size of hazard maps
produced in INETER has been an A0 size. In Japan, the Mt. Fuji case used a multiple
layer type of hazard maps that had multiple volcanic hazard phenomena in one sheet.
The display of many lines was disrupting interpretation; therefore, in this Study, the intensive line expression was avoided.
Considering the above situations, the Study Team concluded to prepared the hazard
maps in one size for all the phenomena in the following structure.
(1)
Map 1: Only lava flow is included. Geology map is included to facilitate understandings on volcanic hazard (A0 size).
(2)
Map 2: Three types of phenomena were included: An overlay display of tephra
fall and lahar and volcanic bomb (A0 size)
(3)
Map 2: Only ash fall is included (A0 size).
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5)
Information Included
Examples of information to be included for the maps are listed in Table 8-7. Since the
targeted users are municipal officials and the staffs in the Civil Defense, the pieces of
information to be included are limited in the following items to have an intelligible
structure.
•
•
•
•
•
•
•
Title
Explanation of volcanic phenomenon
Description of hazard
Photographs and illustration of volcanic phenomena for educational purpose
Project name, year, contact
Logo marks of INETER and JICA
Location guide map for volcano
Table 8-7
Information Required for Hazard Mapping
Basic knowledge on volcanic activities
Information provider
Volcanic cycle
Volcanic phenomena
Volcanic disaster
Responsible entity (Publisher
Contact
Date of publication
Characteristics of the volcano
History of volcanic activities
Types of volcanic disasters within the
scope
Types of volcanic disasters out of the
scope
Disaster prediction results
Location
Name
Contact
Disaster Prediction
Disaster prevention base
Evacuation information
Emergency action agenda
Transportation information
Methods of communication, information collection and dissemination
Surveillance establishment for
volcanic activities
6)
Emergency contacts
Emergency goods
Knowledge in an emergency
Major roads
Emergency transport routes
Transportation restriction
Contacts and locations of related organizations
Contacts for reporting abnormal phenomena
Types
Location
The Draft Hazard Map
The draft hazard map is shown in the following figure.
226
Figure 8-29 Geology (top) and Lava Flow (bottom)
The photographs are Volcano Kilauea (Hawaii's) showing low viscosity basalt lava
flows
227